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Monthly Notices of the Royal Astronomical Society
Journal Prestige (SJR): 2.346
Citation Impact (citeScore): 4
Number of Followers: 15  
 
  Hybrid Journal Hybrid journal (It can contain Open Access articles)
ISSN (Print) 0035-8711 - ISSN (Online) 1365-2966
Published by Oxford University Press Homepage  [425 journals]
  • PeVatron candidate SNR G106.3+2.7 in a low-density cavity: a
           multiwavelength test

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      Pages: 5487 - 5494
      Abstract: ABSTRACTIn this paper, we constrain the density of the interstellar medium (ISM) around the hadronic PeVatron candidate, supernova remnant (SNR) G106.3+2.7, based on X-ray and γ-ray observations. The purpose of this investigation is to understand the influence of the gaseous environment on this SNR as a proton PeVatron candidate. By modelling the self-regulated propagation of the cosmic rays (CRs) injected from the SNR, we calculate the γ-ray emission of CRs via the hadronuclear interactions with the molecular cloud and the ISM, and use the measured γ-ray flux to constrain the ISM density around the SNR. Our results support the picture that the SNR is expanding into a low-density ($\lt 0.05\, {\rm cm}^{-3}$) cavity, enabling the SNR to be a potential proton PeVatron despite that it is presently not in the very early phase.
      PubDate: Mon, 08 Jan 2024 00:00:00 GMT
      DOI: 10.1093/mnras/stae058
      Issue No: Vol. 528, No. 4 (2024)
       
  • New candidate hypervelocity red clump stars in the inner Galactic bulge

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      Pages: 5495 - 5510
      Abstract: ABSTRACTWe search for high-velocity stars in the inner region of the Galactic bulge using a selected sample of red clump stars. Some of those stars might be considered hypervelocity stars (HVSs). Even though the HVSs ejection relies on an interaction with the supermassive black hole (SMBH) at the centre of the Galaxy, there are no confirmed detections of HVSs in the inner region of our Galaxy. With the detection of HVSs, ejection mechanism models can be constrained by exploring the stellar dynamics in the Galactic centre through a recent stellar interaction with the SMBH. Based on a previously developed methodology by our group, we searched with a sample of preliminary data from version 2 of the Vista Variables in the Via Lactea (VVV) Infrared Astrometric Catalogue (VIRAC2) and Gaia DR3 data, including accurate optical and near-infrared proper motions. This search resulted in a sample of 46 stars with transverse velocities larger than the local escape velocity within the Galactic bulge, of which four are prime candidate HVSs with high-proper motions consistent with being ejections from the Galactic centre. Adding to that, we studied a sample of reddened stars without a Gaia DR3 counterpart and found 481 stars with transverse velocities larger than the local escape velocity, from which 65 stars have proper motions pointing out of the Galactic centre and are candidate HVSs. In total, we found 69 candidate HVSs pointing away from the Galactic centre with transverse velocities larger than the local escape velocity.
      PubDate: Sat, 13 Jan 2024 00:00:00 GMT
      DOI: 10.1093/mnras/stae128
      Issue No: Vol. 528, No. 4 (2024)
       
  • Modelling stellar variability in archival HARPS data: I - Rotation and
           activity properties with multidimensional Gaussian processes

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      Pages: 5511 - 5527
      Abstract: ABSTRACTAlthough instruments for measuring the radial velocities (RVs) of stars now routinely reach sub-metre per second accuracy, the detection of low-mass planets is still very challenging. The rotational modulation and evolution of spots and/or faculae can induce variations in the RVs at the level of a few m s–1 in Sun-like stars. To overcome this, a multidimensional Gaussian Process framework has been developed to model the stellar activity signal using spectroscopic activity indicators together with the RVs. A recently published computationally efficient implementation of this framework, S + LEAF 2, enables the rapid analysis of large samples of targets with sizeable data sets. In this work, we apply this framework to HARPS observations of 268 well-observed targets with precisely determined stellar parameters. Our long-term goal is to quantify the effectiveness of this framework to model and mitigate activity signals for stars of different spectral types and activity levels. In this first paper in the series, we initially focus on the activity indicators (S-index and Bisector Inverse Slope), and use them to (a) measure rotation periods for 49 slow rotators in our sample, (b) explore the impact of these results on the spin-down of middle-aged late F, G, and K stars, and (c) explore indirectly how the spot to facular ratio varies across our sample. Our results should provide valuable clues for planning future RV planet surveys such as the Terra Hunting Experiment or the PLATO ground-based follow-up observations programme, and help fine-tune current stellar structure and evolution models.
      PubDate: Sat, 13 Jan 2024 00:00:00 GMT
      DOI: 10.1093/mnras/stae137
      Issue No: Vol. 528, No. 4 (2024)
       
  • Shock-driven synchrotron radio emission from the 2021 outburst of RS
           Ophiuchi

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      Pages: 5528 - 5536
      Abstract: ABSTRACTWe present low-frequency radio observations of the Galactic symbiotic recurrent nova RS Ophiuchi during its 2021 outburst. The observations were carried out with the upgraded Giant Metrewave Radio Telescope spanning a frequency range of 0.15–1.4 GHz during 23–287 d post the outburst. The average value of the optically thin spectral index is α ∼ −0.4 (Fν ∝ να), indicating a non-thermal origin of the radio emission at the observed frequencies. The radio light curves are best represented by shock-driven synchrotron emission, initially absorbed by a clumpy ionized circumbinary medium. We estimate the mass-loss rate of the red giant companion star to be $\dot{M} \sim$ 7.5 × 10−8 M⊙ yr−1 for an assumed stellar wind velocity of 20 km s−1. The 0.15–1.4 GHz radio light curves of the 2021 outburst are systematically brighter than those of the 2006 outburst. Considering similar shock properties between the two outbursts, this is indicative of a relatively higher particle number density in the synchrotron emitting plasma in the current outburst.
      PubDate: Mon, 22 Jan 2024 00:00:00 GMT
      DOI: 10.1093/mnras/stae201
      Issue No: Vol. 528, No. 4 (2024)
       
  • New-generation maximum entropy method: a Lagrangian-based algorithm for
           dynamic reconstruction of interferometric data

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      Pages: 5537 - 5557
      Abstract: ABSTRACTImaging interferometric data in radio astronomy requires the use of non-linear algorithms that rely on different assumptions on the source structure and may produce non-unique results. This is especially true for very long baseline interferometry (VLBI) observations, where the sampling of Fourier space is very sparse. A basic tenet in standard VLBI imaging techniques is to assume that the observed source structure does not evolve during the observation. However, the recent VLBI results of the supermassive black hole at our Galactic Centre (Sagittarius A*), recently reported by the Event Horizon Telescope Collaboration, require the development of dynamic imaging algorithms, since it exhibits variability at minute time-scales. In this paper, we introduce a new non-convex optimization problem that extends the standard maximum entropy method (MEM), for reconstructing intra-observation dynamical images from interferometric data that evolve in every integration time. We present a rigorous mathematical formalism to solve the problem via the primal–dual approach. We build a Newton strategy and we give its numerical complexity. We also give a strategy to iteratively improve the obtained solution and, finally, we define a novel figure of merit to evaluate the quality of the recovered solution. Then, we test the algorithm, called the new-generation MEM (ngMEM), in different synthetic data sets, with increasing difficulty. Finally, we compare it with another well-established dynamical imaging method. Within this comparison, we have identified a significant improvement of the ngMEM reconstructions. Moreover, the evaluation of the integration time evolution scheme and the time contribution showed that this method can play a crucial role in obtaining good dynamic reconstructions.
      PubDate: Mon, 22 Jan 2024 00:00:00 GMT
      DOI: 10.1093/mnras/stae234
      Issue No: Vol. 528, No. 4 (2024)
       
  • The limitations (and potential) of non-parametric morphology statistics
           for post-merger identification

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      Pages: 5558 - 5585
      Abstract: ABSTRACTNon-parametric morphology statistics have been used for decades to classify galaxies into morphological types and identify mergers in an automated way. In this work, we assess how reliably we can identify galaxy post-mergers with non-parametric morphology statistics. Low-redshift (z ≲ 0.2), recent (tpost-merger ≲ 200 Myr), and isolated (r > 100 kpc) post-merger galaxies are drawn from the IllustrisTNG100-1 cosmological simulation. Synthetic r-band images of the mergers are generated with SKIRT9 and degraded to various image qualities, adding observational effects such as sky noise and atmospheric blurring. We find that even in perfect quality imaging, the individual non-parametric morphology statistics fail to recover more than 55 per cent of the post-mergers, and that this number decreases precipitously with worsening image qualities. The realistic distributions of galaxy properties in IllustrisTNG allow us to show that merger samples assembled using individual morphology statistics are biased towards low-mass, high gas fraction, and high mass ratio. However, combining all of the morphology statistics together using either a linear discriminant analysis or random forest algorithm increases the completeness and purity of the identified merger samples and mitigates bias with various galaxy properties. For example, we show that in imaging similar to that of the 10-yr depth of the Legacy Survey of Space and Time, a random forest can identify 89 per cent of mergers with a false positive rate of 17 per cent. Finally, we conduct a detailed study of the effect of viewing angle on merger observability and find that there may be an upper limit to merger recovery due to the orientation of merger features with respect to the observer.
      PubDate: Mon, 29 Jan 2024 00:00:00 GMT
      DOI: 10.1093/mnras/stae287
      Issue No: Vol. 528, No. 4 (2024)
       
  • Accurate Fourier-space statistics for line intensity mapping: Cartesian
           grid sampling without aliased power

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      Pages: 5586 - 5600
      Abstract: ABSTRACTEstimators for n-point clustering statistics in Fourier-space demand that modern surveys of large-scale structure be transformed to Cartesian coordinates to perform Fast Fourier Transforms (FFTs). In this work, we explore this transformation in the context of pixelized line intensity maps (LIM), highlighting potential biasing effects on power-spectrum measurements. Current analyses often avoid a complete resampling of the data by approximating survey geometry as rectangular in Cartesian space, an increasingly inaccurate assumption for modern wide-sky surveys. Our simulations of a $20\, {\times }\, 20\, \text{deg}^2$ 21 cm LIM survey at $0.34\, {\lt }\, z\, {\lt }\, 0.54$ show this assumption biases power-spectrum measurements by ${\gt }\, 20~{{\ \rm per\ cent}}$ across all scales. We therefore present a more robust framework for regridding the voxel intensities on to a 3D FFT field by coordinate transforming large numbers of Monte-Carlo sampling particles. Whilst this unbiases power-spectrum measurements on large scales, smaller scale discrepancies remain, caused by structure smoothing and aliasing from separations unresolved by the grid. To correct these effects, we introduce modelling techniques, higher order particle assignments, and interlaced FFT grids to suppress the aliased power. Using a piecewise cubic spline (PCS) particle assignment and an interlaced FFT field, we achieve sub-per cent accuracy up to 80 per cent of the Nyquist frequency for our 21 cm LIM simulations. We find a more subtle hierarchical improvement in results for higher order assignment schemes, relative to the gains made for galaxy surveys, which we attribute to the extra complexity in LIM from additional discretizing steps. python code accompanying this paper is available at github.com/stevecunnington/gridimp.
      PubDate: Thu, 01 Feb 2024 00:00:00 GMT
      DOI: 10.1093/mnras/stae333
      Issue No: Vol. 528, No. 4 (2024)
       
  • On the role of minor neutrals in determining the characteristic features
           of the Venus ionosphere at low altitudes

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      Pages: 5601 - 5611
      Abstract: ABSTRACTElectron density profiles obtained from radio occultation experiments reveal significant ionization occurring at altitudes below 120 km in the Venusian ionosphere. The presence of such ionization remains unexplained when considering only major neutrals and the resulting ion chemistry. In this study, we investigate the role of minor neutrals, including NO, O2, C, Ar, H2, and H, in the lower altitudes of the Venusian ionosphere using a one-dimensional photochemical model and Akatsuki radio science measurements. We derive the density of minor neutrals from the profiles of major neutrals. Our analysis demonstrates that NO+ and O$_2^+$ ions exhibit a notable presence below 140 km. When we incorporate the minor neutrals, electron density increases below 115 km but remains unchanged above this altitude. Specifically, the density of NO+ increases below 125 km, with corresponding reductions in O$_2^+$. The increase in NO+ above 115 km can be attributed to the charge-exchange reaction between O$_2^+$ and NO. However, below 115 km, the photoionization of NO results in a net increase in NO+ and electron density. These findings highlight the significant role played by minor neutrals, particularly below 115 km, in shaping the Venusian ionosphere at low altitudes.
      PubDate: Fri, 02 Feb 2024 00:00:00 GMT
      DOI: 10.1093/mnras/stae339
      Issue No: Vol. 528, No. 4 (2024)
       
  • Examining baryonic Faber–Jackson relation in galaxy groups

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      Pages: 5612 - 5623
      Abstract: ABSTRACTWe investigate the baryonic Faber–Jackson relation (BFJR), examining the correlation between baryonic mass and velocity dispersion in galaxy groups and clusters. Originally analysed in elliptical galaxies, the BFJR is derivable from the empirical radial acceleration relation (RAR) and MOdified Newtonian Dynamics (MOND), both showcasing a characteristic acceleration scale $\mathrm{g}_\mathrm{\dagger }=1.2\times 10^{-10}\, \mathrm{m}\, \mathrm{s}^{-2}$. Recent interpretations within MOND suggest that galaxy group dynamics can be explained solely by baryonic mass, hinting at a BFJR with g† in these systems. To explore this BFJR, we combined X-ray and optical measurements for 6 galaxy clusters and 13 groups, calculating baryonic masses by combining X-ray gas and stellar mass estimates. Simultaneously, we computed spatially resolved velocity dispersion profiles from membership data using the biweight scale in radial bins. Our results indicate that the BFJR in galaxy groups, using total velocity dispersion, aligns with MOND predictions. Conversely, galaxy clusters exhibit a parallel BFJR with a larger acceleration scale. Analysis using tail velocity dispersion in galaxy groups shows a leftward deviation from the BFJR. Additionally, stacked velocity dispersion profiles reveal two distinct types: declining and flat, based on two parallel BFJRs. The declining profile, if not due to the anisotropy parameters or the incomplete membership, suggests a deviation from standard dark matter (DM) density profiles. We further identify three galaxy groups with unusually low DM fractions.
      PubDate: Fri, 02 Feb 2024 00:00:00 GMT
      DOI: 10.1093/mnras/stae343
      Issue No: Vol. 528, No. 4 (2024)
       
  • Deeper than DEEP: a spectroscopic survey of z > 3 Ly α emitters in
           the Extended Groth Strip

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      Pages: 5624 - 5632
      Abstract: ABSTRACTWe present a spectroscopic survey of Ly α emitters in the Extended Groth Strip (EGS) field, targeting the regime near the Epoch of Reionization. Using Keck/DEep Imaging Multi-Object Spectrograph, we observed 947 high-z candidates with photometric redshifts from 3 < zphot < 7 and down to an H-band (Hubble Space Telescope/Wide Field Camera 3 F160W) magnitude limit of <27.5. Observations were taken over the course of eight nights, with integration times ranging from 4 to 7.8 h. Our survey secured 137 unique redshifts, 126 of which are Ly α emitters at 2.8 < z < 6.3 with a mean redshift of $\overline{z} = 4.3$. We provide a comprehensive redshift catalogue for our targets, as well as the reduced one- and two-dimensional spectra for each object. These observations will provide an important auxiliary data set for the JWST Directors Discretionary Early Release Science programme the Cosmic Evolution Early Release Science Survey, which recently completed near- and mid-infrared imaging and spectroscopy of galaxies in the EGS field.
      PubDate: Mon, 05 Feb 2024 00:00:00 GMT
      DOI: 10.1093/mnras/stae361
      Issue No: Vol. 528, No. 4 (2024)
       
  • Search for brown dwarfs in IC 1396 with Subaru HSC: interpreting the
           impact of environmental factors on substellar population

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      Pages: 5633 - 5648
      Abstract: ABSTRACTYoung stellar clusters are predominantly the hub of star formation and hence, ideal to perform comprehensive studies over the least explored substellar regime. Various unanswered questions like the mass distribution in brown dwarf regime and the effect of diverse cluster environment on brown dwarf formation efficiency still plague the scientific community. The nearby young cluster, IC 1396 with its feedback-driven environment, is ideal to conduct such study. In this paper, we adopt a multiwavelength approach, using deep Subaru HSC along with other data sets and machine learning techniques to identify the cluster members complete down to ∼ 0.03 M⊙ in the central 22 arcmin area of IC 1396. We identify 458 cluster members including 62 brown dwarfs which are used to determine mass distribution in the region. We obtain a star-to-brown dwarf ratio of ∼ 6 for a stellar mass range 0.03–1 M⊙ in the studied cluster. The brown dwarf fraction is observed to increase across the cluster as radial distance from the central OB-stars increases. This study also compiles 15 young stellar clusters to check the variation of star-to-brown dwarf ratio relative to stellar density and ultraviolet (UV) flux ranging within 4–2500 stars pc−2 and 0.7–7.3 G0, respectively. The brown dwarf fraction is observed to increase with stellar density but the results about the influence of incident UV flux are inconclusive within this range. This is the deepest study of IC 1396 as of yet and it will pave the way to understand various aspects of brown dwarfs using spectroscopic observations in future.
      PubDate: Mon, 05 Feb 2024 00:00:00 GMT
      DOI: 10.1093/mnras/stae369
      Issue No: Vol. 528, No. 4 (2024)
       
  • Prospects for detecting proto-neutron star rotation and spin-down using
           supernova neutrinos

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      Pages: 5649 - 5666
      Abstract: ABSTRACTAfter a successful supernova, a proto-neutron star (PNS) cools by emitting neutrinos on ∼1–100 s time-scales. Provided that there are neutrino emission ‘hotspots’ or ‘cold-spots’ on the surface of the rotating PNS, we can expect a periodic modulation in the number of neutrinos observable by detectors. We show that Fourier transform techniques can be used to determine the PNS rotation rate from the neutrino arrival times. Provided there is no spin-down, a 1-parameter Discrete Fourier Transform (DFT) is sufficient to determine the spin period of the PNS. If the PNS is born as a magnetar with polar magnetic field strength B0 ≳ 1015 G and is ‘slowly’ rotating with an initial spin period ≳100 ms, then it can spin-down to periods of the order of seconds during the cooling phase. We propose a modified DFT technique with three frequency parameters to detect spin-down. Due to lack of neutrino data from a nearby supernova except the ∼20 neutrinos detected from SN1987A, we use toy models and one physically motivated modulating function to generate neutrino arrival times. We use the false alarm rate (FAR) to quantify the significance of the Fourier power spectrum peaks. We show that PNS rotation and spin-down are detected with $\rm FAR\,\lt\, 2~{{\ \rm per\ cent}}$ (2σ) for periodic signal content $\rm M\gtrsim 13-15~{{\ \rm per\ cent}}$ if 5 × 103 neutrinos are detected in ∼3 s and with $\rm FAR\,\lt\, 1{{\ \rm per\ cent}}$ for $\rm M\,\ge 5{{\ \rm per\ cent}}$ if 5 × 104 neutrinos are detected in ∼3 s. Since we can expect ∼104−105 neutrino detections from a supernova at 10 kpc, detection of PNS rotation and spin-down is possible using the neutrinos from the next Galactic supernova.
      PubDate: Tue, 06 Feb 2024 00:00:00 GMT
      DOI: 10.1093/mnras/stae378
      Issue No: Vol. 528, No. 4 (2024)
       
  • Observations of interstellar scattering of six pulsars using Polish LOFAR
           station PL611

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      Pages: 5667 - 5678
      Abstract: ABSTRACTWe present the preliminary results of 4 yr of observations of the scattering of pulsar radiation in the interstellar medium using the Low Frequency Array (LOFAR) PL611 station located in Lazy near Krakow. In this work we show the initial results for six pulsars from our observing campaign. We used the HBA antennas of the station, with a central frequency of 154 MHz and a 72 MHz bandwidth and we were able to detect the frequency-dependent change in the pulse profiles. Splitting the bandwidth into a number of separate sub-bands we obtained independent scatter time estimates, which allowed for the estimation of the scattering frequency scaling slope for each individual observation. Our project has been accumulating data for more than 4 yr and as a result we are in a position to study the time variability of the scattering parameters over this period. We detected significant changes in the scatter time and its frequency scaling for at least two of pulsars. The average values of the frequency scaling index for the six pulsars selected for this work are below the range of values predicted by the simple thin screen model of interstellar scattering. This is in accordance with previous results shown for both higher dispersion measure pulsars observed in the past, as well as the more recent LOFAR observations and other projects similar in the observing frequency. We also discuss the advantages of using individual LOFAR stations (or similar instruments) for this kind of research.
      PubDate: Wed, 07 Feb 2024 00:00:00 GMT
      DOI: 10.1093/mnras/stae399
      Issue No: Vol. 528, No. 4 (2024)
       
  • Resolution of the incongruency of dipole asymmetries within various large
           radio surveys – implications for the Cosmological Principle

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      Pages: 5679 - 5691
      Abstract: ABSTRACTWe investigate dipole asymmetries in four large radio surveys, each spanning more than 75 per cent of the sky. Two of them, the Very Large Array Sky Survey (VLASS) and the Rapid ASKAP Continuum Survey (RACS), have recently yielded dipoles that appear incongruent with each other as well as seem inconsistent with previous radio survey dipoles and the cosmic microwave background (CMB) dipole. Because these radio surveys have large overlaps in sky coverage, comprising hence large majority of common radio sources, one would not expect significant differences between their radio dipoles, irrespective of their underlying source of origin. We examine here in detail these radio dipoles, to ascertain the source of incongruency among them. We find the VLASS and RACS data to be containing some declination-dependent systematics, seemingly in the vicinity of the declination limit of each survey. We show that the effects of such systematics can be mitigated by restricting the declination limits of the respective survey during the dipole determination. A weighted mean of the sky coordinates of thus derived dipoles from the four radio surveys lies within 1.2σ of the CMB dipole direction. However, the amplitude appears significantly larger, 3.7 ± 0.6 times or more than the CMB dipole. This puts in doubt not only the conventional wisdom that the genesis of all these dipoles, including that of the CMB dipole, is due to the Solar peculiar motion, it also raises uncomfortable questions about the Cosmological Principle, the basis of the standard ΛCDM cosmological model.
      PubDate: Thu, 08 Feb 2024 00:00:00 GMT
      DOI: 10.1093/mnras/stae414
      Issue No: Vol. 528, No. 4 (2024)
       
  • The radio-loud fraction of quasars at z &gt; 6

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      Pages: 5692 - 5702
      Abstract: ABSTRACTQuasars at redshifts z > 6 are an excellent probe of the formation and evolution of supermassive black holes in the early Universe. The population of radio-luminous quasars is of particular interest, as such quasars could potentially be used to study the neutral intergalactic medium during cosmic reionization via H i 21 cm absorption studies. However, the lack of deep radio observations of z > 6 quasars leaves the population poorly constrained, and suitable candidates for an H i 21 cm absorption study have yet to be found. In this work, we present Jansky Very Large Array (VLA) 1–2 GHz radio continuum observations of 138 quasars at redshifts 6.0 ≤ z < 7.6. We detect the radio continuum emission of the z = 6.1 quasar J1034−1425, with a 1.6 GHz flux density of $170\pm 36\, \mu$Jy. This quasar is radio-quiet with radio-loudness, R ≡ f5 GHz/fν, 4400 Å = 2.4 ± 0.5. In addition, we detect seven other quasars at z > 6, which have previously been characterized in the literature at these frequencies. Using the full sample, we estimate the radio-loud fraction to be $3.8^{+6.2}_{-2.4}\ \hbox{per cent}$, where the uncertainties are 95 per cent confidence intervals. This is lower than recent estimates of the radio-loud fraction in the literature, but is still marginally consistent with no redshift evolution of the radio-loud fraction. We explore the undetected quasar population by stacking their continuum images at their optical positions and obtain a median stacked flux density of 13.8 ± 3.9 µJy and luminosity of log L5 GHz/(W Hz−1) = 24.2 ± 0.1.
      PubDate: Thu, 08 Feb 2024 00:00:00 GMT
      DOI: 10.1093/mnras/stae418
      Issue No: Vol. 528, No. 4 (2024)
       
  • The EBLM Project– XI. Mass, radius, and effective temperature
           measurements for 23 M-dwarf companions to solar-type stars observed with
           CHEOPS

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      Pages: 5703 - 5722
      Abstract: ABSTRACTObservations of low-mass stars have frequently shown a disagreement between observed stellar radii and radii predicted by theoretical stellar structure models. This ‘radius inflation’ problem could have an impact on both stellar and exoplanetary science. We present the final results of our observation programme with the CHaracterising ExOPlanet Satellite (CHEOPS) to obtain high-precision light curves of eclipsing binaries with low-mass stellar companions (EBLMs). Combined with the spectroscopic orbits of the solar-type companions, we can derive the masses, radii, and effective temperatures of 23 M-dwarf stars. We use the pycheops data analysis software to analyse their primary and secondary occultations. For all but one target, we also perform analyses with Transiting Exoplanet Survey Satellite (TESS) light curves for comparison. We have assessed the impact of starspot-induced variation on our derived parameters and account for this in our radius and effective temperature uncertainties using simulated light curves. We observe trends in inflation with both metallicity and orbital separation. We also observe a strong trend in the difference between theoretical and observational effective temperatures with metallicity. There is no such trend with orbital separation. These results are not consistent with the idea that the observed inflation in stellar radius combines with lower effective temperature to preserve the luminosity predicted by low-mass stellar models. Our EBLM systems provide high-quality and homogeneous measurements that can be used in further studies of radius inflation.
      PubDate: Thu, 15 Feb 2024 00:00:00 GMT
      DOI: 10.1093/mnras/stad3866
      Issue No: Vol. 528, No. 4 (2024)
       
  • Discovery of radio eclipses from 4FGL J1646.5−4406: a new candidate
           redback pulsar binary

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      Pages: 5730 - 5741
      Abstract: ABSTRACTLarge widefield surveys make possible the serendipitous discovery of rare subclasses of pulsars. One such class are ‘spider’-type pulsar binaries, comprised of a pulsar in a compact orbit with a low-mass (sub)stellar companion. In a search for circularly polarized radio sources in Australian Square Kilometre Array Pathfinder (ASKAP) Pilot Survey observations, we discovered highly variable and circularly polarized emission from a radio source within the error region of the γ-ray source 4FGL J1646.5−4406. The variability is consistent with the eclipse of a compact, steep-spectrum source behind ablated material from a companion in an ∼5.3 h binary orbit. Based on the eclipse properties and spatial coincidence with 4FGL J1646.5−4406, we argue that the source is likely a recycled pulsar in a ‘redback’ binary system. Using properties of the eclipses from ASKAP and Murchison Widefield Array observations, we provide broad constraints on the properties of the eclipse medium. We identified a potential optical/infrared counterpart in archival data consistent with a variable low-mass star. Using the Parkes radio telescope ‘Murriyang’ and the Meer Karoo Array Telescope (MeerKAT) , we searched extensively for radio pulsations but yielded no viable detections of pulsed emission. We suggest that the non-detection of pulses is due to scattering in the intra-binary material, but scattering from the interstellar medium can also plausibly explain the pulse non-detections if the interstellar dispersion measure exceeds ∼600 pc cm−3. Orbital constraints derived from optical observations of the counterpart would be highly valuable for future γ-ray pulsation searches, which may confirm the source nature as a pulsar.
      PubDate: Mon, 08 Jan 2024 00:00:00 GMT
      DOI: 10.1093/mnras/stae033
      Issue No: Vol. 528, No. 4 (2024)
       
  • Nuclear rings are the inner edge of a gap around the Lindblad Resonance

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      Pages: 5742 - 5762
      Abstract: ABSTRACTGaseous nuclear rings are large-scale coherent structures commonly found at the centres of barred galaxies. We propose that they are an accumulation of gas at the inner edge of an extensive gap that forms around the Inner Lindblad Resonance (ILR). The gap initially opens because the bar potential excites strong trailing waves near the ILR, which remove angular momentum from the gas disc and transport the gas inwards. The gap then widens because the bar potential continuously excites trailing waves at the inner edge of the gap, which remove further angular momentum, moving the edge further inwards until it stops at a distance of several wavelengths from the ILR. The gas accumulating at the inner edge of the gap forms the nuclear ring. The speed at which the gap edge moves and its final distance from the ILR strongly depend on the sound speed, explaining the puzzling dependence of the nuclear ring radius on the sound speed in simulations.
      PubDate: Tue, 16 Jan 2024 00:00:00 GMT
      DOI: 10.1093/mnras/stae082
      Issue No: Vol. 528, No. 4 (2024)
       
  • Mapping dust in the giant molecular cloud Orion A

    • Free pre-print version: Loading...

      Pages: 5763 - 5782
      Abstract: ABSTRACTThe Sun is located close to the Galactic mid-plane, meaning that we observe the Galaxy through significant quantities of dust. Moreover, the vast majority of the Galaxy’s stars also lie in the disc, meaning that dust has an enormous impact on the massive astrometric, photometric and spectroscopic surveys of the Galaxy that are currently underway. To exploit the data from these surveys we require good three-dimensional maps of the Galaxy’s dust. We present a new method for making such maps in which we form the best linear unbiased predictor of the extinction at an arbitrary point based on the extinctions for a set of observed stars. This method allows us to avoid the artificial inhomogeneities (so-called ‘fingers of God’) and resolution limits that are characteristic of many published dust maps. Moreover, it requires minimal assumptions about the statistical properties of the interstellar medium. In fact, we require only a model of the first and second moments of the dust density field. The method is suitable for use with directly measured extinctions, such as those provided by the Rayleigh–Jeans colour excess method, and inferred extinctions, such as those provided by hierarchical Bayesian models like StarHorse. We test our method by mapping dust in the region of the giant molecular cloud Orion A. Our results indicate a foreground dust cloud at a distance of 350 pc, which has been identified in work by another author.
      PubDate: Tue, 30 Jan 2024 00:00:00 GMT
      DOI: 10.1093/mnras/stae268
      Issue No: Vol. 528, No. 4 (2024)
       
  • Evolution of gas flows along the starburst to post-starburst to quiescent
           galaxy sequence

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      Pages: 5783 - 5803
      Abstract: ABSTRACTWe measure velocity offsets in the $\rm{Na {}\rm {\small I}}$ λλ5890, 5896 ($\rm{Na {}\rm {\small D}}$) interstellar medium absorption lines to track how neutral galactic winds change as their host galaxies evolve. Our sample of ∼80 000 SDSS spectra at 0.010 < z < 0.325 includes starburst, post-starburst, and quiescent galaxies, forming an evolutionary sequence of declining star formation rate (SFR). We detect bulk flows across this sequence, mostly at higher host stellar masses (log(M*/M⊙)) > 10). Along this sequence, the fraction of outflows decreases (76 ± 2 per cent to 65 ± 4 per cent to a 3σ upper limit of 34 per cent), and the mean velocity offset changes from outflowing to inflowing (−84.6 ± 5.9 to −71.6 ± 11.4 to $76.6\pm 2.3\, \rm km s^{-1}$). Even within the post-starburst sample, wind speed decreases with time elapsed since the starburst ended. These results reveal that outflows diminish as galaxies age. For post-starbursts, there is evidence for an AGN contribution, especially to the speediest outflows: (1) SFR declines faster in time than outflow velocity, a decoupling arguing against massive stellar feedback; (2) of the few outflows strong enough to escape the interstellar medium (9/105), three of the four hosts with measured emission lines are Seyfert galaxies. For discy starburst galaxies, however, the trends suggest flows out of the stellar disc plane (with outflow 1/2-opening angle > 45°) instead of from the nucleus: the wind velocity decreases as the disc becomes more edge-on, and the outflow fraction, constant at $\sim 90~{{\ \rm per\ cent}}$ for disc inclinations i < 45°, steadily decreases from $\sim 90~{{\ \rm per\ cent}}$ to 20 per cent for i > 45°.
      PubDate: Mon, 05 Feb 2024 00:00:00 GMT
      DOI: 10.1093/mnras/stae366
      Issue No: Vol. 528, No. 4 (2024)
       
  • Compact groups of dwarf galaxies in TNG50: late hierarchical assembly and
           delayed stellar build-up in the low-mass regime

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      Pages: 5804 - 5824
      Abstract: ABSTRACTCompact groups of dwarf galaxies (CGDs) have been observed at low redshifts (z < 0.1) and are direct evidence of hierarchical assembly at low masses. To understand the formation of CGDs and the galaxy assembly in the low-mass regime, we search for analogues of compact (radius ≤100 kpc) groups of dwarfs (7 ≤ log [M*/M⊙] ≤ 9.5) in the IllustrisTNG highest resolution simulation. Our analysis shows that TNG50-1 can successfully produce CGDs at z = 0 with realistic total and stellar masses. We also find that the CGD number density decreases towards the present, especially at z ≲ 0.26, reaching $n \approx 10^{-3.5} \ \rm cMpc^{-3}$ at z = 0. This prediction can be tested observationally with upcoming surveys targeting the faint end of the galaxy population and is essential to constrain galaxy evolution models in the dwarf regime. The majority of simulated groups at z ∼ 0 formed recently ($\lesssim 1.5 \ \rm Gyr$), and CGDs identified at z ≤ 0.5 commonly take more than 1 Gyr to merge completely, giving origin to low- to intermediate-mass (8 ≤ log [M*/M⊙] ≤ 10) normally star-forming galaxies at z = 0. We find that haloes hosting CGDs at z = 0 formed later when compared to haloes of similar mass, having lower stellar masses and higher total gas fractions. The simulations suggest that CGDs observed at z ∼ 0 arise from a late hierarchical assembly in the last ∼3 Gyr, producing rapid growth in total mass relative to stellar mass and creating dwarf groups with median halo masses of $\sim 10^{11.3} \ \rm M_\odot$ and B-band mass-to-light ratios mostly in the range 10 ≲ M/L ≲ 100, in agreement with previous theoretical and observational studies.
      PubDate: Mon, 05 Feb 2024 00:00:00 GMT
      DOI: 10.1093/mnras/stae367
      Issue No: Vol. 528, No. 4 (2024)
       
  • Neutron star mergers and their impact on second generation star formation
           in the early universe

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      Pages: 5825 - 5835
      Abstract: ABSTRACTThe exact evolution of elements in the Universe, from primordial to heavier elements produced via the r-process, is still under scrutiny. The supernova deaths of the very first stars led to the enrichment of their local environments, and can leave behind neutron stars (NSs) as remnants. These remnants can end up in binary systems with other NSs, and eventually merge, allowing for the r-process to occur. We study the scenario where a single NS merger (NSM) enriches a halo early in its evolution to understand the impact on the second generation of stars and their metal abundances. We perform a suite of high-resolution cosmological zoom-in simulations using enzo where we have implemented a new NSM model varying the explosion energy and the delay time. In general, an NSM leads to significant r-process enhancement in the second generation of stars in a galaxy with a stellar mass of ∼105 M⊙ at redshift 10. A high explosion energy leads to a Population II (Pop II) mass fraction of 72 per cent being highly enhanced with r-process elements, while a lower explosion energy leads to 80 per cent being enhanced, but only 14 per cent being highly enhanced. When the NSM has a short delay time of 10 Myr, only 5 per cent of the mass fraction of Pop II stars is highly enhanced, while 64 per cent is highly enhanced for the longest delay time of 100 Myr. This work represents a stepping stone towards understanding how NSMs impact their environments and the metal abundances of descendant generations of stars.
      PubDate: Wed, 07 Feb 2024 00:00:00 GMT
      DOI: 10.1093/mnras/stae397
      Issue No: Vol. 528, No. 4 (2024)
       
  • What if GW190425 did not produce a black hole promptly'

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      Pages: 5836 - 5844
      Abstract: ABSTRACTIt is widely believed that the binary neutron star merger GW190425 produced a black hole promptly upon merger. Motivated by the potential association with the fast radio burst FRB 20190425A, which took place 2.5 h after the merger, we revisit the question of the outcome of GW190425 by means of numerical relativity simulations. We show that current laboratory and astrophysical constraints on the equation of state of dense matter do not rule out the formation of a long-lived remnant. However, the formation of a stable remnant would have produced a bright kilonova, in tension with upper limits by ZTF at the location and time of FRB 20190425A. Moreover, the ejecta would have been optically thick to radio emission for days to months, preventing a putative FRB from propagating out. The predicted dispersion measure is also several orders of magnitude larger than that observed for FRB 20190425A. Our results indicate that FRB 20190425A and GW190425 are not associated. However, we cannot completely rule out the formation of a long-lived remnant, due to the incomplete coverage of the relevant sky regions. More observations of GW190425-like events, including potential upper limit, have the potential to constrain nuclear physics. To this aim, it is important that follow-up observational campaigns of gravitational wave events are informed by the properties of the source, such as their chirp mass, and we urge the LIGO-Virgo-KAGRA collaboration to promptly release them publicly.
      PubDate: Wed, 07 Feb 2024 00:00:00 GMT
      DOI: 10.1093/mnras/stae400
      Issue No: Vol. 528, No. 4 (2024)
       
  • Emergence of the temperature–density relation in the low-density
           intergalactic medium

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      Pages: 5845 - 5851
      Abstract: ABSTRACTWe examine the evolution of the phase diagram of the low-density intergalactic medium during the Epoch of Reionization in simulation boxes with varying reionization histories from the Cosmic Reionization on Computers project. The probability density function (PDF) of gas temperature at fixed density exhibits two clear modes: a warm and a cold temperature mode, corresponding to the gas inside and outside of ionized bubbles. We find that the transition between the two modes is ‘universal’ in the sense that its timing is accurately parametrized by the value of the volume-weighted neutral fraction for any reionization history. This ‘universality’ is more complex than just a reflection of the fact that ionized gas is warm and neutral gas is cold: it holds for the transition at a fixed value of gas density, and gas at different densities transitions from the cold to the warm mode at different values of the neutral fraction, reflecting a non-trivial relationship between the ionization history and the evolving gas density PDF. Furthermore, the ‘emergence’ of the tight temperature–density relation in the warm mode is also approximately ‘universally’ controlled by the volume-weighted neutral fraction for any reionization history. In particular, the ‘emergence’ of the temperature–density relation (as quantified by the rapid decrease in its width) occurs when the neutral fraction is 10−4 ≲ XH i ≲ 10−3 for any reionization history. Our results indicate that the neutral fraction is a primary quantity controlling the various properties of the temperature–density relation, regardless of reionization history.
      PubDate: Tue, 06 Feb 2024 00:00:00 GMT
      DOI: 10.1093/mnras/stae401
      Issue No: Vol. 528, No. 4 (2024)
       
  • The SAMI galaxy survey: predicting kinematic morphology with logistic
           regression

    • Free pre-print version: Loading...

      Pages: 5852 - 5863
      Abstract: ABSTRACTWe use the SAMI (Sydney-AAO Multi-object Integral field spectrograph) galaxy survey to study the the kinematic morphology–density relation: the observation that the fraction of slow rotator galaxies increases towards dense environments. We build a logistic regression model to quantitatively study the dependence of kinematic morphology (whether a galaxy is a fast or slow rotator) on a wide range of parameters, without resorting to binning the data. Our model uses a combination of stellar mass, star formation rate (SFR), r-band half-light radius, and a binary variable based on whether the galaxy’s observed ellipticity (ϵ) is less than 0.4. We show that, at fixed mass, size, SFR, and ϵ, a galaxy’s local environmental surface density (log10(Σ5/Mpc−2)) gives no further information about whether a galaxy is a slow rotator, that is, the observed kinematic–morphology density relation can be entirely explained by the well-known correlations between environment and other quantities. We show how our model can be applied to different galaxy surveys to predict the fraction of slow rotators which would be observed and discuss its implications for the formation pathways of slow rotators.
      PubDate: Thu, 08 Feb 2024 00:00:00 GMT
      DOI: 10.1093/mnras/stae409
      Issue No: Vol. 528, No. 4 (2024)
       
  • Interacting galaxies in the IllustrisTNG simulations – VII: the
           connection between the most luminous active galactic nuclei and galaxy
           interactions

    • Free pre-print version: Loading...

      Pages: 5864 - 5879
      Abstract: ABSTRACTWe investigate the connection between the most luminous active galactic nuclei (AGN), galaxy pairs, and post-mergers in the IllustrisTNG simulation. We select galaxy pairs and post-mergers with a mass ratio between 1:10 < μ < 1:1 and a redshift between 0 < z < 1. We compare the incidence of luminous AGN in pairs with matched non-pair controls, finding that AGN with luminosity Lbol > 1044 erg s−1 occur in ∼26 per cent of paired galaxies with a companion within 20 kpc, compared with ∼14 per cent in controls (a fractional excess of ∼2). The enhancement of AGN in galaxy pairs is luminosity dependent, with the highest excess (a factor of ∼6 ± 2 at the closest separations) for AGN with Lbol > 1045 erg s−1. Additionally, pairs exhibit a modest yet statistically significant excess of luminous AGN up to ∼150 kpc in separation. For pairs which merge between 0 < z < 1, AGN fractions are elevated between 1.5 Gyr before and after coalescence, with the highest excess closest to coalescence. Our results indicate that pre-coalescence interactions drive excesses of luminous AGN, but that luminous AGN in galaxy pairs are not ubiquitous. Finally, we investigate what fraction of AGN can be associated with an interaction (either having a companion within 100 kpc or a merger within the last 500 Myr). For AGN with Lbol > 1045 erg s−1, ∼55 per cent are interacting, compared with a 30 per cent interaction fraction in AGN with 1044 < Lbol < 1044.5 erg s−1. Our results support a picture in which interactions play a dominant role in (but are not the sole cause of) triggering the most luminous AGN.
      PubDate: Mon, 12 Feb 2024 00:00:00 GMT
      DOI: 10.1093/mnras/stae419
      Issue No: Vol. 528, No. 4 (2024)
       
  • Gaia GraL: Gaia DR2 gravitational lens systems – VIII. A radio
           census of lensed systems

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      Pages: 5880 - 5889
      Abstract: ABSTRACTWe present radio observations of 24 confirmed and candidate strongly lensed quasars identified by the Gaia Gravitational Lenses working group. We detect radio emission from eight systems in 5.5 and 9 GHz observations with the Australia Telescope Compact Array (ATCA), and 12 systems in 6 GHz observations with the Karl G. Jansky Very Large Array (VLA). The resolution of our ATCA observations is insufficient to resolve the radio emission into multiple lensed images, but we do detect multiple images from 11 VLA targets. We have analysed these systems using our observations in conjunction with existing optical measurements, including measuring offsets between the radio and optical positions for each image and building updated lens models. These observations significantly expand the existing sample of lensed radio quasars, suggest that most lensed systems are detectable at radio wavelengths with targeted observations, and demonstrate the feasibility of population studies with high-resolution radio imaging.
      PubDate: Thu, 11 Jan 2024 00:00:00 GMT
      DOI: 10.1093/mnras/stad4002
      Issue No: Vol. 528, No. 4 (2024)
       
  • Astroconformer: The prospects of analysing stellar light curves with
           transformer-based deep learning models

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      Pages: 5890 - 5903
      Abstract: ABSTRACTStellar light curves contain valuable information about oscillations and granulation, offering insights into stars’ internal structures and evolutionary states. Traditional asteroseismic techniques, primarily focused on power spectral analysis, often overlook the crucial phase information in these light curves. Addressing this gap, recent machine learning applications, particularly those using Convolutional Neural Networks (CNNs), have made strides in inferring stellar properties from light curves. However, CNNs are limited by their localized feature extraction capabilities. In response, we introduce Astroconformer, a Transformer-based deep learning framework, specifically designed to capture long-range dependencies in stellar light curves. Our empirical analysis centres on estimating surface gravity (log g), using a data set derived from single-quarter Kepler light curves with log g values ranging from 0.2 to 4.4. Astroconformer demonstrates superior performance, achieving a root-mean-square-error (RMSE) of 0.017 dex at log g ≈ 3 in data-rich regimes and up to 0.1 dex in sparser areas. This performance surpasses both K-nearest neighbour models and advanced CNNs. Ablation studies highlight the influence of receptive field size on model effectiveness, with larger fields correlating to improved results. Astroconformer also excels in extracting νmax with high precision. It achieves less than 2 per cent relative median absolute error for 90-d red giant light curves. Notably, the error remains under 3 per cent for 30-d light curves, whose oscillations are undetectable by a conventional pipeline in 30 per cent cases. Furthermore, the attention mechanisms in Astroconformer align closely with the characteristics of stellar oscillations and granulation observed in light curves.
      PubDate: Wed, 10 Jan 2024 00:00:00 GMT
      DOI: 10.1093/mnras/stae068
      Issue No: Vol. 528, No. 4 (2024)
       
  • Stability of dusty rings in protoplanetary discs

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      Pages: 5904 - 5923
      Abstract: ABSTRACTDust rings in protoplanetary discs are often observed in thermal dust emission and could be favourable environments for planet formation. While dust rings readily form in gas pressure maxima, their long-term stability is key to both their observability and potential to assist in planet formation. We investigate the stability of the dust ring generated by interactions of a protoplanetary disc with a Neptune-sized planet and consider its possible long-term evolution using the FARGO3D Multifluid code. We look at the onset of the Rossby Wave Instability (RWI) and compare how the addition of dust in a disc can alter the stability of the gas phase. We find that with the addition of dust, the rings generated by planet–disc interactions are more prone to RWI and can cause the gas phase to become unstable. The instability is shown to occur more easily for higher Stokes number dust, as it accumulates into a more narrow ring which triggers the RWI, while the initial dust fraction plays a more minor role in the stability properties. We show that the dusty RWI generates vortices that collect dust in their cores, which could be sites for further planetesimal formation. We conclude that the addition of dust can cause a ring in a protoplanetary disc to become more prone to instability leading to a different long-term evolution compared to gas-only simulations of the RWI.
      PubDate: Wed, 10 Jan 2024 00:00:00 GMT
      DOI: 10.1093/mnras/stae089
      Issue No: Vol. 528, No. 4 (2024)
       
  • Search for interacting galaxy clusters from SDSS DR-17 employing optimized
           friends-of-friends algorithm and multimessenger tracers

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      Pages: 5924 - 5951
      Abstract: ABSTRACTIn the theoretical framework of hierarchical structure formation, galaxy clusters evolve through continuous accretion and mergers of substructures. Cosmological simulations have revealed the best picture of the universe as a 3D filamentary network of dark-matter distribution called the cosmic web. Galaxy clusters are found to form at the nodes of this network and are the regions of high merging activity. Such mergers being highly energetic, contain a wealth of information about the dynamical evolution of structures in the Universe. Observational validation of this scenario needs a colossal effort to identify numerous events from all-sky surveys. Therefore, such efforts are sparse in literature and tend to focus on individual systems. In this work, we present an improved search algorithm for identifying interacting galaxy clusters and have successfully produced a comprehensive list of systems from SDSS DR-17. By proposing a set of physically motivated criteria, we classified these interacting clusters into two broad classes, ‘merging’ and ‘pre-merging/postmerging’ systems. Interestingly, as predicted by simulations, we found that most cases show cluster interaction along the prominent cosmic filaments of galaxy distribution (i.e. the proxy for dark matter filaments), with the most violent ones at their nodes. Moreover, we traced the imprint of interactions through multiband signatures, such as diffuse cluster emissions in radio or X-rays. Although we could not find direct evidence of diffuse emission from connecting filaments and ridges; our catalogue of interacting clusters will ease locating such faintest emissions as data from sensitive telescopes such as eROSITA or SKA, becomes accessible.
      PubDate: Wed, 17 Jan 2024 00:00:00 GMT
      DOI: 10.1093/mnras/stae200
      Issue No: Vol. 528, No. 4 (2024)
       
  • A practical guide to a moment approach for neutrino transport in numerical
           relativity

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      Pages: 5952 - 5971
      Abstract: ABSTRACTThe development of a neutrino moment-based radiative-transfer code to simulate binary neutron star mergers can easily become an obstacle path because of the numerous ways in which the solution of the equations may fail. We describe the implementation of the grey M1 scheme in our fully general-relativistic magnetohydrodynamics code and detail those choices and strategies that could lead either to a robust scheme or to a series of failures. In addition, we present new tests designed to show the consistency and accuracy of our code in conditions that are similar to realistic merging conditions and introduce a new, publicly available, benchmark based on the head-on collision of two neutron stars. This test, which is computationally less expensive than a complete merging binary but has all the potential pitfalls of the full scenario, can be used to compare future implementations of M1 schemes with the one presented here.
      PubDate: Sat, 27 Jan 2024 00:00:00 GMT
      DOI: 10.1093/mnras/stae224
      Issue No: Vol. 528, No. 4 (2024)
       
  • X-ray variability of SDSS quasars based on the SRG/eROSITA all-sky survey

    • Free pre-print version: Loading...

      Pages: 5972 - 5989
      Abstract: ABSTRACTWe examine the long-term (rest-frame time-scales from a few months to ∼20 yr) X-ray variability of a sample of 2344 X-ray bright quasars from the Sloan Digital Sky Survey (SDSS) data release 14 quasar (DR14Q) catalogue, based on the data of the Spectrum-Roentgen-Gamma (SRG)/eROSITA All-Sky Survey complemented for ∼7 per cent of the sample by archival data from the XMM–Newton Serendipitous Source Catalogue. We characterize variability by a structure function, SF2(Δt). We confirm the previously known anticorrelation of the X-ray variability amplitude with luminosity. We also study the dependence of X-ray variability on black hole mass, MBH, and on an X-ray-based proxy of the Eddington ratio, λX. Less massive black holes prove to be more variable for given Eddington ratio and time-scale. X-ray variability also grows with decreasing Eddington ratio and becomes particularly strong at λX of less than a few per cent. We confirm that the X-ray variability amplitude increases with increasing time-scale. The SF2(Δt) dependence can be satisfactorily described by a power law, with the slope ranging from ∼0 to ∼0.4 for different (MBH, λX) subsamples (except for the subsample with the lowest black hole mass and Eddington ratio, where it is equal to 1.1 ± 0.4).
      PubDate: Wed, 24 Jan 2024 00:00:00 GMT
      DOI: 10.1093/mnras/stae261
      Issue No: Vol. 528, No. 4 (2024)
       
  • Broad-band study of gamma-ray blazars at redshifts z = 2.0–2.5

    • Free pre-print version: Loading...

      Pages: 5990 - 6009
      Abstract: ABSTRACTHigh redshift blazars are among the most powerful non-explosive sources in the Universe and play a crucial role in understanding the evolution of relativistic jets. To understand these bright objects, we performed a detailed investigation of the multiwavelength properties of 79 γ-ray blazars with redshifts ranging from z = 2.0 to 2.5, using data from Fermi LAT, Swift XRT/UVOT, and NuSTAR observations. In the γ-ray band, the spectral analysis revealed a wide range of flux and photon indices, from 5.32 × 10−10 to 3.40 × 10−7 photon cm−2 s−1 and from 1.66 to 3.15, respectively, highlighting the diverse nature of these sources. The detailed temporal analysis showed that flaring activities were observed in 31 sources. Sources such as 4C+71.07, PKS 1329-049, and 4C + 01.02, demonstrated significant increase in the γ-ray luminosity and flux variations, reaching peak luminosity exceeding 1050 erg s−1. The temporal analysis extended to X-ray and optical/ultraviolet (UV) bands, showed clear flux changes in some sources in different observations. The time-averaged properties of high redshift blazars were derived through modeling the spectral energy distributions with a one-zone leptonic scenario, assuming the emission region is within the broad-line region (BLR) and the X-ray and γ-ray emissions are due to inverse Compton scattering of synchrotron and BLR-reflected photons. This modeling allowed us to constrain the emitting particle distribution, estimate the magnetic field inside the jet, and evaluate the jet luminosity, which is discussed in comparison with the disc luminosity derived from fitting the excess in the UV band.
      PubDate: Wed, 31 Jan 2024 00:00:00 GMT
      DOI: 10.1093/mnras/stae273
      Issue No: Vol. 528, No. 4 (2024)
       
  • Measuring M31 globular cluster ages and metallicities using both
           photometry and spectroscopy

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      Pages: 6010 - 6024
      Abstract: ABSTRACTThe ages and metallicities of globular clusters play an important role not just in testing models for their formation and evolution but also in understanding the assembly history of their host galaxies. Here, we use a combination of imaging and spectroscopy to measure the ages and metallicities of globular clusters in M31, the closest massive galaxy to our own. We use the strength of the near-infrared calcium triplet spectral feature to provide a relatively age-insensitive prior on the metallicity when fitting stellar population models to the observed photometry. While the age–extinction degeneracy is an issue for globular clusters projected on to the disc of M31, we find generally old ages for globular clusters in the halo of M31 and in its satellite galaxy NGC 205 in line with previous studies. We measure ages for a number of outer halo globular clusters for the first time, finding that globular clusters associated with halo substructure extend to younger ages and higher metallicities than those associated with the smooth halo. This is in line with the expectation that the smooth halo was accreted earlier than the substructured halo.
      PubDate: Sat, 27 Jan 2024 00:00:00 GMT
      DOI: 10.1093/mnras/stae282
      Issue No: Vol. 528, No. 4 (2024)
       
  • Rotation plays a role in the generation of magnetic fields in single white
           dwarfs

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      Pages: 6056 - 6074
      Abstract: ABSTRACTRecent surveys of close white dwarf binaries as well as single white dwarfs have provided evidence for the late appearance of magnetic fields in white dwarfs, and a possible generation mechanism, a crystallization and rotation-driven dynamo has been suggested. A key prediction of this dynamo is that magnetic white dwarfs rotate, at least on average, faster than their non-magnetic counterparts and/or that the magnetic field strength increases with rotation. Here we present rotation periods of ten white dwarfs within 40 pc measured using photometric variations. Eight of the light curves come from TESS observations and are thus not biased towards short periods, in contrast to most period estimates that have been reported previously in the literature. These TESS spin periods are indeed systematically shorter than those of non-magnetic white dwarfs. This means that the crystallization and rotation-driven dynamo could be responsible for a fraction of the magnetic fields in white dwarfs. However, the full sample of magnetic white dwarfs also contains slowly rotating strongly magnetic white dwarfs which indicates that another mechanism that leads to the late appearance of magnetic white dwarfs might be at work, either in addition to or instead of the dynamo. The fast-spinning and massive magnetic white dwarfs that appear in the literature form a small fraction of magnetic white dwarfs, and probably result from a channel related to white dwarf mergers.
      PubDate: Wed, 31 Jan 2024 00:00:00 GMT
      DOI: 10.1093/mnras/stae307
      Issue No: Vol. 528, No. 4 (2024)
       
  • Influence of temperature on the chemical evolution and desorption of pure
           CO ices irradiated by cosmic-rays analogues

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      Pages: 6075 - 6098
      Abstract: ABSTRACTCarbon monoxide (CO) plays a vital role in interstellar chemistry, existing abundantly in both gaseous and frozen environments. Understanding the radiation-driven chemistry of CO-rich ices is crucial for comprehending the formation and desorption of C-bearing molecules in the interstellar medium (ISM), particularly considering the potential impact of temperature on these processes. We report experimental data on irradiation processing of pure CO ice by cosmic ray analogues (95.2 MeV 136Xe23+ ions) at temperatures of 10, 15, and 20 K, in the IGLIAS set-up coupled to the IRRSUD beamline at GANIL (Caen, France). The evolution of the irradiated frozen samples was monitored by infrared spectroscopy. The computational PROCODA code allows us to quantify the chemical evolution of the samples, determining effective reaction rates coefficients (ERCs), molecular abundances at the chemical equilibrium (CE) phase, and desorption processes. The model integrated 18 chemical species – 8 observed (CO, CO2, C3, O3, C2O, C3O, C3O2, and C5O3) and 10 non-observed but predicted (C, O, C2, O2, CO3, C4O, C5O, C2O2, C2O3, C4O2) – linked via 156 reactions. Our findings reveal temperature-driven influences on molecular abundances at chemical equilibrium, desorption yields and rates, and ERC values. Certain reaction routes exhibit distinct thermochemical behaviours of gas- and ice-phase reactions which may be attributed to the presence of neighbouring molecules within the ice matrix. This study provides pivotal insights into the chemical evolution of CO-enriched ice under irradiation, impacting solid-state astrochemistry, clarifying molecular abundances, and advancing our understanding of ISM chemistry and temperature effects on ionized radiation-processed frozen ices.
      PubDate: Fri, 02 Feb 2024 00:00:00 GMT
      DOI: 10.1093/mnras/stae313
      Issue No: Vol. 528, No. 4 (2024)
       
  • H ii regions and diffuse ionized gas in the AMUSING++ Compilation –
           I. Catalogue presentation

    • Free pre-print version: Loading...

      Pages: 6099 - 6118
      Abstract: ABSTRACTWe present a catalogue of ∼52 000 extragalactic H ii regions and their spectroscopic properties obtained using Integral Field Spectroscopy (IFS) from MUSE observations. The sample analysed in this study contains 678 galaxies within the nearby Universe (0.004 <z < 0.06) covering different morphological types and a wide range of stellar masses (6 < log(M*/M⊙) < 13). Each galaxy was analysed using the pipe3d and pyhiiextractor codes to obtain information of the ionized gas and underlying stellar populations. Specifically, the fluxes, equivalent widths, velocities and velocity dispersions of 30 emission lines covering the wavelength range between λ4750 to λ9300 Å, were extracted and were used to estimate luminosity weighted ages and metallicities of the underlying stellar populations from each H ii region (of the original sample we detect H ii regions in 539 galaxies). In addition, we introduce and apply a novel method and independent of any intrinsic physical property to estimate and decontaminate the contribution of the diffuse ionized gas. Using the final catalogue, we explore the dependence of properties of the H ii regions on different local and global galaxy parameters: (i) Hubble type, (ii) stellar mass, (iii) galactocentric distance, and (iv) the age and metallicity of the underlying/neighbour stellar populations. We confirm known relations between properties of the H ii regions and the underlying stellar populations (in particular, with the age) uncovered using data of lower spatial and spectral resolution. Furthermore, we describe the existence of two main families of diffuse ionized gas different for galaxies host or not of H ii regions.
      PubDate: Mon, 05 Feb 2024 00:00:00 GMT
      DOI: 10.1093/mnras/stae345
      Issue No: Vol. 528, No. 4 (2024)
       
  • Effective viscosity, resistivity, and Reynolds number in weakly
           collisional plasma turbulence

    • Free pre-print version: Loading...

      Pages: 6119 - 6128
      Abstract: ABSTRACTWe examine dissipation and energy conversion in weakly collisional plasma turbulence, employing in situ observations from the Magnetospheric Multiscale mission and kinetic particle-in-cell simulations of proton–electron plasma. A previous result indicated the presence of viscous-like and resistive-like scaling of average energy conversion rates – analogous to scalings characteristic of collisional systems. This allows for extraction of collisional-like coefficients of effective viscosity and resistivity, and thus also determination of effective Reynolds numbers based on these coefficients. The effective Reynolds number, as a measure of the available bandwidth for turbulence to populate various scales, links turbulence macroscale properties with kinetic plasma properties in a novel way.
      PubDate: Fri, 02 Feb 2024 00:00:00 GMT
      DOI: 10.1093/mnras/stae355
      Issue No: Vol. 528, No. 4 (2024)
       
  • Correction to: Fundamental parameters for 45 open clusters with Gaia DR2,
           an improved extinction correction and a metallicity gradient prior

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      Pages: 6129 - 6129
      Abstract: errata, addendaopen clusters and associations: general
      PubDate: Mon, 19 Feb 2024 00:00:00 GMT
      DOI: 10.1093/mnras/stae363
      Issue No: Vol. 528, No. 4 (2024)
       
  • Migration of low-mass planets in inviscid discs: the effect of radiation
           transport on the dynamical corotation torque

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      Pages: 6130 - 6140
      Abstract: ABSTRACTLow-mass planets migrate in the type-I regime. In the inviscid limit, the contrast between the vortensity trapped inside the planet’s corotating region and the background disc vortensity leads to a dynamical corotation torque, which is thought to slow down inward migration. We investigate the effect of radiative cooling on low-mass planet migration using inviscid 2D hydrodynamical simulations. We find that cooling induces a baroclinic forcing on material U-turning near the planet, resulting in vortensity growth in the corotating region, which in turn weakens the dynamical corotation torque and leads to 2–3× faster inward migration. This mechanism is most efficient when cooling acts on a time-scale similar to the U-turn time of material inside the corotating region, but is none the less relevant for a substantial radial range in a typical disc (R ∼ 5–50 au). As the planet migrates inwards, the contrast between the vortensity inside and outside the corotating region increases and partially regulates the effect of baroclinic forcing. As a secondary effect, we show that radiative damping can further weaken the vortensity barrier created by the planet’s spiral shocks, supporting inward migration. Finally, we highlight that a self-consistent treatment of radiative diffusion as opposed to local cooling is critical in order to avoid overestimating the vortensity growth and the resulting migration rate.
      PubDate: Sat, 10 Feb 2024 00:00:00 GMT
      DOI: 10.1093/mnras/stae372
      Issue No: Vol. 528, No. 4 (2024)
       
  • The VLBA CANDELS GOODS-North Survey. II – Wide-field source catalogue
           comparison between the VLBA, EVN, e-MERLIN, and VLA

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      Pages: 6141 - 6158
      Abstract: ABSTRACTDeep radio surveys of extragalactic legacy fields trace a large range of spatial and brightness temperature sensitivity scales, and therefore have differing biases to radio-emitting physical components within galaxies. This is particularly true of radio surveys performed at $\lesssim 1 \ \mathrm{arcsec}$ angular resolutions, and so robust comparisons are necessary to better understand the biases present in each survey. We present a multiresolution and multiwavelength analysis of the sources detected in a new Very Long Baseline Array (VLBA) survey of the Cosmic Assembly Near-IR Deep Extragalactic Legacy Survey Great Observatories Origins Deep Survey-North field. For the 24 VLBA-selected sources described in Paper I, we augment the VLBA data with EVN data, and ∼0.1–1 arcsec angular resolution data provided by Very Large Array (VLA) and enhanced-Multi Element Remotely Linked Interferometry Network. This sample includes new active galactic nuclei (AGN) detected in this field, thanks to a new source extraction technique that adopts priors from ancillary multiwavelength data. The high brightness temperatures of these sources (TB ≳ 106 K) confirm AGN cores, that would often be missed or ambiguous in lower-resolution radio data of the same sources. Furthermore, only 15 sources are identified as ‘radiative’ AGN based on available X-ray and infrared constraints. By combining VLA and VLBA measurements, we find evidence that the majority of the extended radio emission is also AGN dominated, with only three sources with evidence for extended potentially star formation-dominated radio emission. We demonstrate the importance of wide-field multiresolution (arcsecond–milliarcsecond) coverage of the faint radio source population, for a complete picture of the multiscale processes within these galaxies.
      PubDate: Tue, 06 Feb 2024 00:00:00 GMT
      DOI: 10.1093/mnras/stae381
      Issue No: Vol. 528, No. 4 (2024)
       
  • MUSE-ALMA Haloes X: the stellar masses of gas-rich absorbing galaxies

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      Pages: 6159 - 6166
      Abstract: ABSTRACTThe physical processes by which gas is accreted onto galaxies, transformed into stars, and then expelled from galaxies are of paramount importance to galaxy evolution studies. Observationally constraining each of these baryonic components in the same system, however, is challenging. Furthermore, simulations indicate that the stellar mass of galaxies is a key factor influencing CGM properties. Indeed, absorption lines detected against background quasars offer the most compelling way to study the cold gas in the circumgalactic medium (CGM). The MUSE-ALMA Haloes survey is composed of quasar fields covered with VLT/MUSE observations, comprising 32 H i absorbers at 0.2 < z < 1.4 and 79 associated galaxies, with available or upcoming molecular gas measurements from ALMA. We use a dedicated 40-orbit HST UVIS and IR WFC3 broad-band imaging campaign to characterize the stellar content of these galaxies. By fitting their spectral energy distribution, we establish they probe a wide range of stellar masses: 8.1 < log (M*/M⊙) < 12.4. Given their star formation rates, most of these objects lie on the main sequence of galaxies. We also confirm a previously reported anticorrelation between the stellar masses and CGM hydrogen column density N (H i), indicating an evolutionary trend where higher mass galaxies are less likely to host large amounts of H i gas in their immediate vicinity up to 120 kpc. Together with other studies from the MUSE-ALMA Haloes survey, these data provide stellar masses of absorber hosts, a key component of galaxy formation and evolution, and observational constraints on the relation between galaxies and their surrounding medium.
      PubDate: Wed, 07 Feb 2024 00:00:00 GMT
      DOI: 10.1093/mnras/stae387
      Issue No: Vol. 528, No. 4 (2024)
       
  • Spectral and timing evolution of GX 340+0 along its Z-track

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      Pages: 6167 - 6175
      Abstract: ABSTRACTWe present the results from spectral and timing study of the Z source GX 340+0 using AstroSat’s SXT and LAXPC data. During the observation the source traced out the complete Z-track, allowing for the spectral evolution study of the horizontal, normal, and flaring branches (HB, NB, and FB) as well as the hard and soft apexes (HA and SA). The spectra are better and more physically described by a blackbody component and a hot Comptonizing corona with a varying covering fraction, rather than one having a disc component. Along the track, the Comptonized flux (as well as the covering fraction) monotonically decreases. It is the blackbody component (both the temperature and radius) which varies non-monotonically and hence gives rise to the Z-track behaviour. Rapid timing study reveals a prominent quasi-periodic oscillation (QPO) at ∼50 Hz at the HB, HA, and upper NB, while a QPO at ∼6 Hz is seen for the other branches. The fractional rms of the QPOs increase with energy and exhibit soft lags in all branches except SA and FB.
      PubDate: Wed, 07 Feb 2024 00:00:00 GMT
      DOI: 10.1093/mnras/stae389
      Issue No: Vol. 528, No. 4 (2024)
       
  • AT2020ohl: its nature and probable implications

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      Pages: 6176 - 6192
      Abstract: ABSTRACTASASSN-20hx, a.k.a AT2020ohl, is an ambiguous nuclear transient, which was discovered in the nearby galaxy NGC6297 by the All-Sky Automated Survey for Supernovae. We have investigated the evolution of AT2020ohl using a multiwavelength data set to explain the geometry of the system and the energy radiated by it between X-ray and radio wavelengths. Our X-ray, UV/optical, and radio observations of the object jointly clarify the association of AT2020ohl with the nuclear activity of NGC6297. We detected radio counterpart of AT2020ohl 111 and 313 d after the discovery in Jansky Very Large Array X-band with flux densities 47 ± 14 and 34 ± 3 $\mu$Jy, respectively. Using multiwavelength data analysis, we nullify the possibility of associating any stellar disruption process with this event. We found some evidence showing that the host galaxy is a merger remnant, so the possibility of a binary supermassive black hole (SMBH) system cannot be ruled out. The central SMBH has a mass of ∼1.2 × 107 M⊙. We propose the accretion disc activity as the origin of AT2020ohl – it is either due to disc accretion event on to the central SMBH or due to the sudden accretion activity in a pre-existing accretion disc of the system during the interaction of two SMBHs which became gravitationally bound during a merger process. However, we also admit that with the existing data set, it is impossible to say definitively, among these two probabilities, which one is the origin of this nuclear transient.
      PubDate: Fri, 09 Feb 2024 00:00:00 GMT
      DOI: 10.1093/mnras/stae395
      Issue No: Vol. 528, No. 4 (2024)
       
  • Collisions of red giants in galactic nuclei

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      Pages: 6193 - 6209
      Abstract: ABSTRACTIn stellar-dense environments, stars can collide with each other. For collisions close to a supermassive black hole (SMBH), the collisional kinetic energy can be so large that the colliding stars can be destroyed, potentially releasing an amount of energy comparable to that of a supernova. These black hole-driven disruptive collisions have been examined mostly analytically, with the non-linear hydrodynamical effects being left largely unstudied. Using the moving-mesh hydrodynamics code arepo, we investigate high-velocity (>103 km s−1) collisions between 1 M⊙ giants with varying radii, impact parameters, and initial approaching velocities, and estimate their observables. Very strong shocks across the collision surface efficiently convert ${\gtrsim} 10~{{\ \rm per\ cent}}$ of the initial kinetic energy into radiation energy. The outcome is a gas cloud expanding supersonically, homologously, and quasi-spherically, generating a flare with a peak luminosity ≃1041–1044 erg s−1 in the extreme ultraviolet band (≃10 eV). The luminosity decreases approximately following a power law of t−0.7 initially, then t−0.4 after t ≃ 10 d at which point it would be bright in the optical band (≲1eV). Subsequent, and possibly even brighter, emission would be generated due to the accretion of the gas cloud on to the nearby SMBH, possibly lasting up to multiyear time-scales. This inevitable BH–collision product interaction can contribute to the growth of BHs at all mass scales, in particular, seed BHs at high redshifts. Furthermore, the proximity of the events to the central BH makes them a potential tool for probing the existence of dormant BHs, even very massive ones which cannot be probed by tidal disruption events.
      PubDate: Wed, 07 Feb 2024 00:00:00 GMT
      DOI: 10.1093/mnras/stae396
      Issue No: Vol. 528, No. 4 (2024)
       
  • Correction to: How limiting is optical follow-up for fast radio burst
           applications' Forecasts for radio and optical surveys

    • Free pre-print version: Loading...

      Pages: 6210 - 6210
      Abstract: This is a correction to: Joscha N. Jahns-Schindler, Laura G. Spitler, Charles R. H. Walker, Carlton M. Baugh, How limiting is optical follow-up for fast radio burst applications' Forecasts for radio and optical surveys, Monthly Notices of the Royal Astronomical Society, Volume 523, Issue 4, August 2023, Pages 5006–5023, https://doi.org/10.1093/mnras/stad1659.
      PubDate: Mon, 19 Feb 2024 00:00:00 GMT
      DOI: 10.1093/mnras/stae415
      Issue No: Vol. 528, No. 4 (2024)
       
  • The frequency and mass-ratio distribution of binaries in clusters II:
           radial segregation in the nearby dissolving open clusters Hyades and
           Praesepe

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      Pages: 6211 - 6220
      Abstract: ABSTRACTWe have determined the mass functions, mass-ratio distribution functions, and fractions of binary stars with mass ratios above particular thresholds for radially separated populations of stars in the nearby open clusters Hyades and Praesepe. Radial mass segregation is detected, with the populations of stars within the tidal radii having much flatter mass functions than those outside the tidal radii. Within the tidal radii, the frequency of binary stars with mass ratio q > 0.5 is 50–75 per cent higher for Hyades and 5–30 per cent higher for Praesepe. We also, for the first time, detect mass-ratio radial segregation. Of the binaries for which q > 0.5, ∼80 per cent of the inner Hyades population also have q > 0.75, while for the extra-tidal population, the ratio is ∼50 per cent. For Praesepe, ∼67 per cent of the inner sample have q > 0.75, and 35–45 per cent of the outer sample.
      PubDate: Fri, 09 Feb 2024 00:00:00 GMT
      DOI: 10.1093/mnras/stae425
      Issue No: Vol. 528, No. 4 (2024)
       
  • Correction to: Retrieval study of cool, directly imaged exoplanet 51 Eri b

    • Free pre-print version: Loading...

      Pages: 6221 - 6221
      Abstract: This is a correction to: Niall Whiteford, Alistair Glasse, Katy L. Chubb, Daniel Kitzmann, Shrishmoy Ray, Mark W. Phillips, Beth A. Biller, Paul I. Palmer, Ken Rice, Ingo P. Waldmann, Quentin Changeat, Nour Skaf, Jason Wang, Billy Edwards, Ahmed Al-Refaie, Retrieval study of cool, directly imaged exoplanet 51 Eri b, Monthly Notices of the Royal Astronomical Society, Volume 525, Issue 1, October 2023, Pages 1375–1400, https://doi.org/10.1093/mnras/stad670.
      PubDate: Mon, 19 Feb 2024 00:00:00 GMT
      DOI: 10.1093/mnras/stad3076
      Issue No: Vol. 528, No. 4 (2024)
       
  • On the cusp of cusps: a universal model for extreme scattering events in
           the ISM

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      Pages: 6292 - 6301
      Abstract: ABSTRACTThe scattering structures in the interstellar medium responsible for so-called extreme scattering events (ESEs), observed in quasars and pulsars, remain enigmatic. Current models struggle to explain the high-frequency light curves of ESEs, and a recent analysis of a double lensing event in PSR B0834+06 reveals features of ESEs that may also be challenging to accommodate via existing models. We propose that these features arise naturally when the lens has a cusp-like profile, described by the elementary A3 cusp catastrophe. This is an extension of previous work describing pulsar scintillation as arising from A2 fold catastrophes in thin, corrugated plasma sheets along the line of sight. We call this framework of describing the lens potentials via elementary catastrophes ‘doubly catastrophic lensing’, as catastrophes (e.g. folds and cusps) have long been used to describe universal features in the light curves of lensing events that generically manifest, regardless of the precise details of the lens. Here, we argue that the lenses themselves may be described by these same elementary structures. If correct, the doubly catastrophic lensing framework would provide a unified description of scintillation and ESEs, where the lenses responsible for these scattering phenomena are universal and can be fully described by a small number of unfolding parameters. This could enable their application as giant cosmic lenses for precision measurements of coherent sources, including fast radio bursts and pulsars.
      PubDate: Wed, 31 Jan 2024 00:00:00 GMT
      DOI: 10.1093/mnras/stae300
      Issue No: Vol. 528, No. 4 (2024)
       
  • Small-scale radio jets and tidal disruption events: a theory of
           high-luminosity compact symmetric objects

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      Pages: 6302 - 6311
      Abstract: ABSTRACTDouble lobe radio sources associated with active galactic nuclei represent one of the longest studied groups in radio astronomy. A particular subgroup of double radio sources comprises the compact symmetric objects (CSOs). CSOs are distinguished by their prominent double structure and subkpc total size. It has been argued that the vast majority of high-luminosity CSOs (CSO 2s) represent a distinct class of active galactic nuclei with its own morphological structure and lifecycle. In this work, we present theoretical considerations regarding CSO 2s. We develop a semi-analytic evolutionary model, inspired by the results of large-scale numerical simulations of relativistic jets, that reproduces the features of the radio source population. We show that CSO 2s may be generated by finite energy injections and propose stellar tidal disruption events as a possible cause. We find that tidal disruption events of giant branch stars with masses ≳1 M⊙ can fuel these sources and discuss possible approaches to confirming this hypothesis. We predict that if the tidal disruption scenario holds, CSO 2s with sizes less than 400 pc should outnumber larger sources by more than a factor of 10. Our results motivate future numerical studies to determine whether the scenarios we consider for fuelling and source evolution can explain the observed radio morphologies. Multiwavelength observational campaigns directed at these sources will also provide critical insight into the origins of these objects, their environments, and their lifespans.
      PubDate: Thu, 01 Feb 2024 00:00:00 GMT
      DOI: 10.1093/mnras/stae322
      Issue No: Vol. 528, No. 4 (2024)
       
  • The minimal sizes of impactors that formed the Vesta family and 15 other
           asteroid families

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      Pages: 6312 - 6318
      Abstract: AbstractThe minimal sizes of impactors that produced asteroid families were calculated, and their maximal sizes, i.e. the size that corresponds to head-on collisions, were estimated. We used data for 16 large families and the physical parameters of some members of these families available in NASA's JPL updated in 2022. We found that the typical minimal sizes of family-forming impactors were of the order of one-tenth the size of the parent bodies (PBs). The Themis family, for which the ratio of the radii rimp/RPB = 0.08 and the mass loss is as large as 0.55, presents an example. The families of Juno and Euphrosyne, with the impactor to PB size ratio of an order of 0.01, are rather exceptional. The PBs of Juno and Euphrosyne families lost only 0.0014 and 0.0061 of their mass, respectively. It was found that the double structure of the Vesta family could have originated from two impacts by the bodies with radii as small as about 4 km, at least.
      PubDate: Thu, 01 Feb 2024 00:00:00 GMT
      DOI: 10.1093/mnras/stae332
      Issue No: Vol. 528, No. 4 (2024)
       
  • Rapid neutron star cooling triggered by dark matter

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      Pages: 6319 - 6328
      Abstract: ABSTRACTWe study the effect of asymmetric fermionic dark matter (DM) on the thermal evolution of neutron stars (NSs). No interaction between DM and baryonic matter is assumed, except the gravitational one. Using the two-fluid formalism, we show that DM accumulated in the core of a star pulls inwards the outer baryonic layers of the star, increasing the baryonic density in the NS core. As a result, it significantly affects the star’s thermal evolution by triggering an early onset of the direct Urca (DU) process and modifying the photon emission from the surface caused by the decrease of the radius. Thus, due to the gravitational pull of DM, the DU process becomes kinematically allowed for stars with lower masses. Based on these results, we discuss the importance of NS observations at different distances from the Galactic Centre. Since the DM distribution peaks towards the Galactic Centre, NSs in this region are expected to contain higher DM fractions that could lead to a different cooling behavior.
      PubDate: Thu, 01 Feb 2024 00:00:00 GMT
      DOI: 10.1093/mnras/stae337
      Issue No: Vol. 528, No. 4 (2024)
       
  • An environment-dependent halo mass function as a driver for the early
           quenching of z ≥ 1.5 cluster galaxies

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      Pages: 6329 - 6339
      Abstract: ABSTRACTMany z ≈1.5 galaxies with a stellar mass (M⋆) $\ge 10^{10}\, \mathrm{M}_\odot$ are already quenched in both galaxy clusters (>50 per cent) and the field (>20 per cent), with clusters having a higher quenched fraction at all stellar masses compared to the field. A puzzling issue is that these massive quenched galaxies have stellar populations of similar age in both clusters and the field. This suggests that, despite the higher quenched fraction in clusters, the dominant quenching mechanism for massive galaxies is similar in both environments. In this work, we use data from the cosmological hydrodynamic simulations Hydrangea and EAGLE to test whether the excess quenched fraction of massive galaxies in z=1.5 clusters results from fundamental differences in their halo properties compared to the field. We find that (i) at $10^{10}\le \, M_{\star }/\mathrm{M}_\odot \, \le 10^{11}$, quenched fractions at 1.5<z<3.5 are consistently higher for galaxies with higher peak maximum circular velocity of the dark matter halo (vmax, peak), and (ii) the distribution of vmax, peak is strongly biased towards higher values for cluster satellites compared to the field centrals. Due to this difference in the halo properties of cluster and field galaxies, secular processes alone may account for (most of) the environmental excess of massive quenched galaxies in high-redshift (proto-)clusters. Taken at face value, our results challenge a fundamental assumption of popular quenching models that clusters are assembled from an unbiased subset of infalling field galaxies. If confirmed, this would imply that such models must necessarily fail at high redshift, as indicated by recent observations.
      PubDate: Fri, 02 Feb 2024 00:00:00 GMT
      DOI: 10.1093/mnras/stae341
      Issue No: Vol. 528, No. 4 (2024)
       
  • A search for millisecond radio bursts from Messier 82

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      Pages: 6340 - 6346
      Abstract: ABSTRACTFast radio bursts (FRBs) are short-duration radio pulses of cosmological origin. Among the most common sources predicted to explain this phenomenon are bright pulses from a class of extremely highly magnetized neutron stars known as magnetars. Motivated by the discovery of an FRB-like pulse from the Galactic magnetar SGR 1935+2154, we searched for similar events in Messier 82 (M82). With a star formation rate 40 times that of the Milky Way, one might expect that the implied rate of events similar to that seen from SGR 1935+2154 from M82 should be 40 times higher than that of the Milky Way. We observed M82 at 1.4 GHz with the 20-m telescope at the Green Bank Observatory for 34.8 d. While we found many candidate events, none had a signal-to-noise ratio greater than 8. We also show that there are insufficient numbers of repeating low-significance events at similar dispersion measures to constitute a statistically significant detection. From these results, we place an upper bound for the rate of radio pulses from M82 to be 30 yr−1 above a fluence limit of 8.5 Jy ms. While this is less than nine times the rate of radio bursts from magnetars in the Milky Way inferred from the previous radio detections of SGR 1935+2154, it is possible that propagation effects from interstellar scattering are currently limiting our ability to detect sources in M82. Further searches of M82 and other nearby galaxies are encouraged to probe this putative FRB population.
      PubDate: Mon, 05 Feb 2024 00:00:00 GMT
      DOI: 10.1093/mnras/stae344
      Issue No: Vol. 528, No. 4 (2024)
       
  • Stark broadening data for ultraviolet lines of Ni v

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      Pages: 6347 - 6353
      Abstract: ABSTRACTWe provide in this work Stark broadening data (widths and shifts) for 120 ultraviolet spectral lines of Ni v ion. Our calculations are performed using the semiclassical perturbation method. For energy levels and oscillator strength calculations, we use the multiconfiguration Hatree–Fock approach. Stark shifts and widths are calculated for collisions with electrons and with the positive ions: H+, He+, and He++, allowing us to take into account the important perturbers in stellar atmospheres. We compare our Stark widths with estimations obtained using the Cowley formula. Our electron impact Stark widths are also fitted with temperature using a logarithmic formula. Finally, our obtained Stark widths are used to investigate the influence of Stark broadening in the atmospheric conditions of hot DA white dwarfs. Despite the importance of ultraviolet lines of Ni v ion for modelling white dwarf atmospheres and also for investigations of variation of fundamental constants with gravitational potential, we did not find Stark broadening data previously calculated or measured for Ni v ion. The objective of this work is to give the missed data.
      PubDate: Wed, 07 Feb 2024 00:00:00 GMT
      DOI: 10.1093/mnras/stae391
      Issue No: Vol. 528, No. 4 (2024)
       
  • Galaxy stellar and total mass estimation using machine learning

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      Pages: 6354 - 6369
      Abstract: ABSTRACTConventional galaxy mass estimation methods suffer from model assumptions and degeneracies. Machine learning (ML), which reduces the reliance on such assumptions, can be used to determine how well present-day observations can yield predictions for the distributions of stellar and dark matter. In this work, we use a general sample of galaxies from the TNG100 simulation to investigate the ability of multibranch convolutional neural network (CNN) based ML methods to predict the central (i.e. within 1−2 effective radii) stellar and total masses, and the stellar mass-to-light ratio (M*/L). These models take galaxy images and spatially resolved mean velocity and velocity dispersion maps as inputs. Such CNN-based models can, in general, break the degeneracy between baryonic and dark matter in the sense that the model can make reliable predictions on the individual contributions of each component. For example, with r-band images and two galaxy kinematic maps as inputs, our model predicting M*/L has a prediction uncertainty of 0.04 dex. Moreover, to investigate which (global) features significantly contribute to the correct predictions of the properties above, we utilize a gradient-boosting machine. We find that galaxy luminosity dominates the prediction of all masses in the central regions, with stellar velocity dispersion coming next. We also investigate the main contributing features when predicting stellar and dark matter mass fractions (f*, fDM) and the dark matter mass MDM, and discuss the underlying astrophysics.
      PubDate: Wed, 07 Feb 2024 00:00:00 GMT
      DOI: 10.1093/mnras/stae406
      Issue No: Vol. 528, No. 4 (2024)
       
  • On the evolution of the observed mass-to-length relationship for
           star-forming filaments

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      Pages: 6370 - 6387
      Abstract: ABSTRACTThe interstellar medium is threaded by a hierarchy of filaments from large scales (∼100 pc) to small scales (∼0.1 pc). The masses and lengths of these nested structures may reveal important constraints for cloud formation and evolution, but it is difficult to investigate from an evolutionary perspective using single observations. In this work, we extract simulated molecular clouds from the ‘Cloud Factory’ galactic-scale ISM suite in combination with 3D Monte Carlo radiative transfer code polaris to investigate how filamentary structure evolves over time. We produce synthetic dust continuum observations in three regions with a series of snapshots and use the filfinder algorithm to identify filaments in the dust derived column density maps. When the synthetic filaments mass and length are plotted on an mass–length (M–L) plot, we see a scaling relation of L ∝ M0.45 similar to that seen in observations, and find that the filaments are thermally supercritical. Projection effects systematically affect the masses and lengths measured for the filaments, and are particularly severe in crowded regions. In the filament M–L diagram we identify three main evolutionary mechanisms: accretion, segmentation, and dispersal. In particular we find that the filaments typically evolve from smaller to larger masses in the observational M–L plane, indicating the dominant role of accretion in filament evolution. Moreover, we find a potential correlation between line mass and filament growth rate. Once filaments are actively star forming they then segment into smaller sections, or are dispersed by internal or external forces.
      PubDate: Thu, 08 Feb 2024 00:00:00 GMT
      DOI: 10.1093/mnras/stae407
      Issue No: Vol. 528, No. 4 (2024)
       
  • Studying the nulling, subpulse drifting, and moding in PSR J1921+1948 with
           the FAST

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      Pages: 6388 - 6397
      Abstract: ABSTRACTWe reported the observations of nulling, subpulse drifting, and moding of radio radiation in pulsar (PSR) B1918+19 at 1250 MHz with the Five-hundred-meter Aperture Spherical radio Telescope. The nulling fraction is 2.6 ± 0.1 per cent and no periodicity of nulling can be seen. We confirmed the existence of three different drift modes (A, B, C) and a disordered mode (N) at 1250 MHz. Unlike the other three modes where the second component of the average pulse profile dominates, the first component of the average pulse profile in mode C is brighter than the other components, the second component shifts forward and the fourth component shifts backward. The bidrifting phenomenon is observed in PSR B1918+19, the drifting of the first and second components is positive, and the drift direction of the fourth component is negative. The drifting rate of the drift bands composed of the first and second components has an obvious evolutionary trend. Mode B has a short duration and no clear trend can be seen. But for mode A, the drift rate of each drift band starts relatively fast, then slows down to a steady state, and finally increases slowly until it enters either null or mode N. Further analysis shows that the emergence and significant variation in the drifting period of multidrifting subpulse emission modes for PSR B1918+19 may be due to the aliasing effect. The interesting subpulse emission phenomenon of PSR B1918+19 at different frequencies provides a unique opportunity to understand the switching mechanism of the multidrift mode of the pulsars.
      PubDate: Thu, 08 Feb 2024 00:00:00 GMT
      DOI: 10.1093/mnras/stae408
      Issue No: Vol. 528, No. 4 (2024)
       
  • Time evolution of X-ray bright points observed with NuSTAR

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      Pages: 6398 - 6410
      Abstract: ABSTRACTWe present analysis on two X-ray bright points observed over several hours during the recent solar minimum (2020 February 21 and 2020 September 12–13) with the Nuclear Spectroscopic Telescope Array (NuSTAR), a sensitive hard X-ray imaging spectrometer. This is so far the most detailed study of bright points in hard X-rays, emission which can be used to search for faint hot and/or non-thermal sources. We investigate the bright points’ time evolution with NuSTAR, and in extreme ultraviolet (EUV) and soft X-rays with Solar Dynamic Observatory/Atmospheric Imaging Assembly (SDO/AIA) and Hinode/X-Ray Telescope. The variability in the X-ray and EUV time profiles is generally not well matched, with NuSTAR detecting spikes that do not appear in EUV. We find that, for the 2020 February bright point, the increased X-ray emission during these spikes is due to material heated to ∼ 4.2–4.4 MK (found from fitting the X-ray spectrum). The 2020 September bright point also shows spikes in the NuSTAR data with no corresponding EUV signature seen by SDO/AIA, though in this case, it was due to an increase in emission measure of material at ∼ 2.6 MK and not a significant temperature change. So, in both cases, the discrepancy is likely due to the different temperature sensitivity of the instruments, with the X-ray variability difficult to detect in EUV due to cooler ambient bright point emission dominating. No non-thermal emission is detected, so we determine upper limits finding that only a steep non-thermal component between 3 and 4 keV could provide the required heating whilst being consistent with a null detection in NuSTAR.
      PubDate: Fri, 09 Feb 2024 00:00:00 GMT
      DOI: 10.1093/mnras/stae417
      Issue No: Vol. 528, No. 4 (2024)
       
  • Rendez-vous with massive interstellar objects, as triggers of
           destabilization

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      Pages: 6411 - 6424
      Abstract: ABSTRACTWe study how close passages of interstellar objects of planetary and substellar masses may affect the immediate and long-term dynamics of the Solar system. We consider two nominal approach orbits, namely the orbits of actual interstellar objects 1I/’Oumuamua and 2I/Borisov, assuming them to be typical or representative for interstellar swarms of matter. Thus, the nominal orbits of the interloper in our models cross the inner part of the Solar system. Series of massive numerical experiments are performed, in which the interloper’s mass is varied with a small step over a broad range. We find that, even if a Jovian-mass interloper does not experience close encounters with the Solar system planets (and this holds for our nominal orbits), our planetary system can be destabilized on time-scales as short as several million years. In what concerns substellar-mass interlopers (free-floating brown dwarfs), an immediate (on a time-scale of ∼10–100 yr) consequence of such a massive interstellar object (MISO) flyby is a sharp increase in the orbital eccentricities and inclinations of the outer planets. On an intermediate time-scale (∼103 to 105 yr after the MISO flyby), Uranus or Neptune can be ejected from the system, as a result of their mutual close encounters and encounters with Saturn. On a secular time-scale (∼106 to 107 yr after the MISO flyby), the perturbation wave formed by secular planetary interactions propagates from the outer Solar system to its inner zone.
      PubDate: Fri, 09 Feb 2024 00:00:00 GMT
      DOI: 10.1093/mnras/stae428
      Issue No: Vol. 528, No. 4 (2024)
       
  • BOSS quasar outflows traced by C iv

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      Pages: 6425 - 6443
      Abstract: ABSTRACTWe investigate possible factors that drive fast quasar outflows using a sample of 39 249 quasars at median redshift 〈z〉 ≈ 2.17. Unique to this study, the quasar redshifts are re-measured based on the Mg ii emission line, and explore unprecedented outflow velocities (>6000 km s−1), while maintaining statistical significance. We measure reliable C iv blueshifts for 1178 quasars with velocities >2500 km s−1. From those, 255(13) quasars have blueshifts above 4000(6000) km s−1, with the highest C iv velocity ≈7000 km s−1. Several correlations are observed, where higher C iv blueshifts in general are in quasars with broader, weaker C iv emission profiles, weak He ii emission, larger Eddington ratios, and bluer ultraviolet (UV) continuum slope across the rest-frame UV to near-infrared. Analysis reveals two primary factors contributing to faster outflows: higher Eddington ratios, and softer far-UV continuum (hν >24.6 eV). We find supporting evidence that radiative line driving may generate extreme outflow velocities, influenced by multiple factors as suggested by the aforementioned correlations. This evidence highlights the importance of considering a multidimensional parameter space in future studies when analyzing large C iv blueshifts to determine the fundamental causes of outflows.
      PubDate: Thu, 15 Feb 2024 00:00:00 GMT
      DOI: 10.1093/mnras/stae429
      Issue No: Vol. 528, No. 4 (2024)
       
  • Effects of heterogeneous data sets and time-lag measurement techniques on
           cosmological parameter constraints from Mg ii and C iv
           reverberation-mapped quasar data

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      Pages: 6444 - 6469
      Abstract: ABSTRACTPreviously, we demonstrated that Mg ii and C iv reverberation-mapped quasars (RM QSOs) are standardizable and that the cosmological parameters inferred using the broad-line region radius–luminosity (R–L) relation are consistent with those determined from better-established cosmological probes. With more data expected from ongoing and future spectroscopic and photometric surveys, it is imperative to examine how new QSO data sets of varied quality, with their own specific luminosity and time-delay distributions, can be best used to determine more restrictive cosmological parameter constraints. In this study, we test the effect of adding 25 OzDES Mg ii RM QSOs as well as 25 lower quality SDSS RM C iv QSOs, which increases the previous sample of RM QSOs by $\sim 36{{\ \rm per\ cent}}$. Although cosmological parameter constraints become tighter for some cosmological models after adding these new QSOs, the new combined data sets have increased differences between R–L parameter values obtained in different cosmological models and thus a lower standardizability for the larger Mg ii + C iv compilation. Different time-delay methodologies, particularly the ICCF and CREAM methods used for inferring time delays of SDSS RM QSOs, slightly affect cosmological and R–L relation parameter values, however, the effect is negligible for (smaller) compilations of robust time-delay detections. Our analysis indicates that increasing the sample size is not sufficient for tightening cosmological constraints and a quality cut is necessary to obtain a standardizable RM QSO sample.
      PubDate: Sat, 10 Feb 2024 00:00:00 GMT
      DOI: 10.1093/mnras/stae433
      Issue No: Vol. 528, No. 4 (2024)
       
  • Sardinia Radio Telescope observations of the Coma cluster

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      Pages: 6470 - 6495
      Abstract: ABSTRACTWe present deep total intensity and polarization observations of the Coma cluster at 1.4 and 6.6 GHz performed with the Sardinia Radio Telescope. By combining the single-dish 1.4 GHz data with archival Very Large Array observations, we obtain new images of the central radio halo and of the peripheral radio relic where we properly recover the brightness from the large-scale structures. At 6.6 GHz, we detect both the relic and the central part of the halo in total intensity and polarization. These are the highest frequency images available to date for these radio sources in this galaxy cluster. In the halo, we find a localized spot of polarized signal, with fractional polarization of about 45 per cent. The polarized emission possibly extends along the north-east side of the diffuse emission. The relic is highly polarized, up to 55 per cent, as usually found for these sources. We confirm the halo spectrum is curved, in agreement with previous single-dish results. The spectral index is α = 1.48 ± 0.07 at a reference frequency of 1 GHz and varies from α ≃ 1.1, at 0.1 GHz, up to α ≃ 1.8, at 10 GHz. We compare the Coma radio halo surface brightness profile at 1.4 GHz (central brightness and e-folding radius) with the same properties of the other haloes, and we find that it has one of the lowest emissivities observed so far. Reanalysing the relic’s spectrum in the light of the new data, we obtain a refined radio Mach number of M = 2.9 ± 0.1.
      PubDate: Sat, 10 Feb 2024 00:00:00 GMT
      DOI: 10.1093/mnras/stae436
      Issue No: Vol. 528, No. 4 (2024)
       
  • Quasar outflow deceleration or acceleration: predictions and a search

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      Pages: 6496 - 6516
      Abstract: ABSTRACTQuasar winds can shock and sweep up ambient interstellar medium (ISM) gas, contributing to galactic quenching. We combine and extend past models of energy-conserving shock bubbles around quasars, investigate model implications from an observational standpoint, and test model predictions using new high-resolution spectroscopic observations of the broad absorption-line quasar SDSS J030000.56+004828.0 (J0300). Even with constant energy input from the wind, a bubble’s expansion decelerates over time as more ISM gas is swept up. Our new observations enable a direct search for this deceleration. We obtain the tightest reported 3σ limit on the average rest-frame deceleration (or acceleration) of a quasar outflow: a < 0.1 km s−1 yr−1 (<3 × 10−4 cm s−2) in the relatively low-velocity Ca ii outflow of J0300 over 9.65 rest-frame years. We can satisfy these limits with certain parameter choices in our model, but the large velocity range of the Ca ii absorption in J0300 rules out the hypothesis that such gas shares the velocity of the swept-up ISM gas in a self-similar shock bubble. We investigate the possibility of ram-pressure acceleration of preexisting ISM clouds and conclude that the velocity range seen in Ca ii in J0300 is potentially consistent with such an explanation. The Ca ii-absorbing gas clouds in J0300 have been inferred to have high densities by Choi et al., in which case they can only have been accelerated to their current speeds if they were originally at least an order of magnitude less dense than they are today.
      PubDate: Wed, 07 Feb 2024 00:00:00 GMT
      DOI: 10.1093/mnras/stae330
      Issue No: Vol. 528, No. 4 (2024)
       
  • The RATT PARROT: serendipitous discovery of a peculiarly scintillating
           pulsar in MeerKAT imaging observations of the Great Saturn – Jupiter
           Conjunction of 2020. I. Dynamic imaging and data analysis

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      Pages: 6517 - 6537
      Abstract: ABSTRACTWe report on a radiopolarimetric observation of the Saturn–Jupiter Great Conjunction of 2020 using the MeerKAT L-band system, initially carried out for science verification purposes, which yielded a serendipitous discovery of a pulsar. The radiation belts of Jupiter are very bright and time variable: coupled with the sensitivity of MeerKAT, this necessitated development of dynamic imaging techniques, reported on in this work. We present a deep radio ‘movie’ revealing Jupiter’s rotating magnetosphere, a radio detection of Callisto, and numerous background radio galaxies. We also detect a bright radio transient in close vicinity to Saturn, lasting approximately 45 min. Follow-up deep imaging observations confirmed this as a faint compact variable radio source, and yielded detections of pulsed emission by the commensal MeerTRAP search engine, establishing the object’s nature as a radio emitting neutron star, designated PSR J2009−2026. A further observation combining deep imaging with the PTUSE pulsar backend measured detailed dynamic spectra for the object. While qualitatively consistent with scintillation, the magnitude of the magnification events and the characteristic time–scales are odd. We are tentatively designating this object a pulsar with anomalous refraction recurring on odd time-scales (PARROT). As part of this investigation, we present a pipeline for detection of variable sources in imaging data, with dynamic spectra and light curves as the products, and compare dynamic spectra obtained from visibility data with those yielded by PTUSE. We discuss MeerKAT’s capabilities and prospects for detecting more of such transients and variables.
      PubDate: Fri, 02 Feb 2024 00:00:00 GMT
      DOI: 10.1093/mnras/stae303
      Issue No: Vol. 528, No. 4 (2024)
       
  • Convergence properties of fine structure constant measurements using
           quasar absorption systems

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      Pages: 6550 - 6558
      Abstract: ABSTRACTSearches for space–time variations of fundamental constants have entered an era of unprecedented precision. New, high-quality quasar spectra require increasingly refined analytical methods. In this paper, a continuation in a series to establish robust and unbiased methodologies, we explore how convergence criteria in non-linear least-squares optimization impact on quasar absorption system measurements of the fine structure constant α. Given previous claims for high-precision constraints, we critically examine the veracity of a so-called blinding approach, in which α is fixed at the terrestrial value during the model building process, releasing it as a free parameter only after the ‘final’ absorption system kinematic structure has been obtained. We show that this approach results in such small consecutive parameter steps during minimization that convergence is unlikely to be reached, even after as many as 1000 iterations. The fix is straightforward: α must be treated as a free parameter from the earliest possible stages of absorption system model building. The implication of the results presented here is that all previous measurements that have used initially fixed α should be reworked.
      PubDate: Mon, 19 Feb 2024 00:00:00 GMT
      DOI: 10.1093/mnras/stae306
      Issue No: Vol. 528, No. 4 (2024)
       
  • Redshift-dependent RSD bias from intrinsic alignment with DESI Year 1
           spectra

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      Pages: 6559 - 6567
      Abstract: ABSTRACTWe estimate the redshift-dependent, anisotropic clustering signal in the Dark Energy Spectroscopic Instrument (DESI) Year 1 Survey created by tidal alignments of Luminous Red Galaxies (LRGs) and a selection-induced galaxy orientation bias. To this end, we measured the correlation between LRG shapes and the tidal field with DESI’s Year 1 redshifts, as traced by LRGs and Emission-Line Galaxies. We also estimate the galaxy orientation bias of LRGs caused by DESI’s aperture-based selection, and find it to increase by a factor of seven between redshifts 0.4−1.1 due to redder, fainter galaxies falling closer to DESI’s imaging selection cuts. These effects combine to dampen measurements of the quadrupole of the correlation function (ξ2) caused by structure growth on scales of 10–80 h−1 Mpc by about 0.15 per cent for low redshifts (0.4 < z < 0.6) and 0.8 per cent for high (0.8 < z < 1.1), a significant fraction of DESI’s error budget. We provide estimates of the ξ2 signal created by intrinsic alignments that can be used to correct this effect, which is necessary to meet DESI’s forecasted precision on measuring the growth rate of structure. While imaging quality varies across DESI’s footprint, we find no significant difference in this effect between imaging regions in the Legacy Imaging Survey.
      PubDate: Mon, 19 Feb 2024 00:00:00 GMT
      DOI: 10.1093/mnras/stae317
      Issue No: Vol. 528, No. 4 (2024)
       
  • Seismology of rubble-pile asteroids in binary systems

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      Pages: 6568 - 6580
      Abstract: ABSTRACTThe mutual gravitational interaction of binary asteroids, which make up approximately 15 per cent of the near-Earth asteroid (NEA) population, provides a continuous tidal force, creating ground motion. We explore the potential of kilometre-sized binary asteroids as targets for seismological studies of their interior structure. We use a numerical model wherein each body is constructed of discrete particles interacting via gravity and contact forces. The system's orbital properties are modelled based on those of typical binary NEAs: a secondary body orbits a primary body at a distance of a few to 10 primary radii, resulting in orbital periods of a few tens of hours. We varied the elastic moduli (stiffness) of the constituent particles and measured a strain of a few micrometres caused by the orbiting satellite. Over eight orbital periods, the acceleration of the strain vector along the primary body's equatorial axis indicates that tidally induced ground motion generated by a binary asteroid system is detectable by modern seismometers, like the instruments deployed on the InSight mission to Mars. Owing to the relatively short orbital period of the satellite – a mean of 25.8 h for known binary NEAs – only a modest mission lifetime would be required for a seismometer to adequately characterize an asteroid's interior through tidally induced deformation. Future deployment of seismometers on binary asteroids will allow for a detailed characterization of the structure of these objects.
      PubDate: Thu, 01 Feb 2024 00:00:00 GMT
      DOI: 10.1093/mnras/stae325
      Issue No: Vol. 528, No. 4 (2024)
       
  • Cloudlet capture model for the accretion streamer onto the disc of DG Tau

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      Pages: 6581 - 6592
      Abstract: ABSTRACTDG Tau is a nearby T Tauri star associated with a collimated jet, a circumstellar disc, and a streamer a few hundred au long. The streamer connects to the disc at ∼50 au from DG Tau. At this location SO emission is observed, likely due to the release of sulphur from dust grains caused by the shock of the impact of the accretion streamer onto the disc. We investigate the possibility that the DG Tau streamer was produced via cloudlet capture on the basis of hydrodynamic simulations, considering a cloudlet initiating infall at 600 au from DG Tau with low angular momentum so that the centrifugal force is smaller than the gravitational force, even at 50 au. The elongation of the cloudlet into a streamer is caused by the tidal force when its initial velocity is much less than the free-fall velocity. The elongated cloudlet reaches the disc and forms a high-density gas clump. Our hydrodynamic model reproduces the morphology and line-of-sight velocity of CS (5 − 4) emission from the northern streamer observed with Atacama Large Millimeter/submillimeter Array. We discuss the conditions for forming a streamer based on the simulations. We also show that the streamer should perturb the disc after impact for several thousands of years.
      PubDate: Thu, 01 Feb 2024 00:00:00 GMT
      DOI: 10.1093/mnras/stae338
      Issue No: Vol. 528, No. 4 (2024)
       
  • Catalogue of nearby blue and near-solar gas metallicity SDSS dwarf
           galaxies

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      Pages: 6593 - 6607
      Abstract: ABSTRACTA less explored aspect of dwarf galaxies is their metallicity evolution. Generally, dwarfs have lower metallicities than Hubble sequence late-type galaxies, but in reality, dwarfs span a wide range of metallicities with several open questions regarding the formation and evolution of the lowest and the highest metallicity dwarfs. We present a catalogue of 3459 blue, nearby, star-forming dwarf galaxies extracted from SDSS DR-16 including calculation of their metallicities using the mean of several calibrators. To compile our catalogue we applied redshift, absolute magnitude, stellar mass, optical diameter, and line flux signal-to-noise criteria. This produced a catalogue from the upper end of the dwarf galaxy stellar mass range. Our catalogued dwarfs have blue g – i colours and Hβ equivalent widths, indicative of having undergone a recent episode of star formation, although their star formation rates (SFRs) suggest only a moderate to low enhancement in star formation, similar to the SFRs in low surface brightness and evolved tidal dwarfs. While the catalogued dwarfs cover a range of metallicities, their mean metallicity is ∼0.2 dex below solar metallicity, indicating relatively chemically evolved galaxies. The vast majority of the catalogue, with clean photometry, are relatively isolated dwarfs with only modest SFRs and a narrow range of g – i colour, consistent with internally driven episodic mild bursts of star formation. The presented catalogue’s robust metallicity estimates for nearby SDSS dwarf galaxies will help target future studies to understand the physical processes driving the metallicity evolution of dwarfs.
      PubDate: Fri, 09 Feb 2024 00:00:00 GMT
      DOI: 10.1093/mnras/stae390
      Issue No: Vol. 528, No. 4 (2024)
       
  • Search for quasi-periodic oscillations in TESS light curves of bright
           Fermi Blazars

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      Pages: 6608 - 6618
      Abstract: ABSTRACTIn a previous paper, we reported evidence for quasi-periodicities in the Transiting Exoplanet Survey Satellite (TESS) light curves of BL Lacerate and two other blazars found serendipitously in the Sloan Digital Sky Survey (SDSS) active galactic nuclei catalogue. In this work, we find tentative evidence for quasi-periodic features in the TESS observations of five sources in the fourth catalogue of the Fermi–Large Area Telescope sources: J090453.4−573503, J2345−1555, B0422+004, J002159.2−514028, and B0537−441. We analysed the TESS light curves of these blazars that we extracted using a customized approach. The quasi-periodic oscillations (QPOs) are searched for using two timing analysis techniques: generalized Lomb–Scargle periodogram and weighted wavelet Z-transform. Their apparent periods lie in the range of 2.8–6.5 d and have at least 3σ significance in both of these methods. QPOs at such time-scales can originate from the kink instability model which relates the quasi-periodic feature with the growth of kinks in the magnetized relativistic jets. We performed Markov Chain Monte Carlo simulations to obtain the posterior distribution of parameters associated with this model and found the kink period consistent with previous studies.
      PubDate: Wed, 07 Feb 2024 00:00:00 GMT
      DOI: 10.1093/mnras/stae410
      Issue No: Vol. 528, No. 4 (2024)
       
  • Devolatilization of extrasolar planetesimals by 60Fe and 26Al heating

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      Pages: 6619 - 6630
      Abstract: ABSTRACTWhilst the formation of Solar system planets is constrained by meteoritic evidence, the geophysical history of low-mass exoplanets is much less clear. The bulk composition and climate states of rocky exoplanets may vary significantly based on the composition and properties of the planetesimals they form. An important factor influenced by planetesimal composition is water content, where the desiccation of accreting planetesimals impacts the final water content of the resultant planets. While the inner planets of the Solar system are comparatively water-poor, recent observational evidence from exoplanet bulk densities and planetary formation models suggests that rocky exoplanets engulfed by substantial layers of high-pressure ices or massive steam atmospheres could be widespread. Here, we quantify variations in planetesimal desiccation due to potential fractionation of the two short-lived radioisotopes 26Al and 60Fe relevant for internal heating on planetary formation time-scales. We focus on how order of magnitude variations in 60Fe can affect the water content of planetesimals, and how this may alter the formation of extrasolar ocean worlds. We find that heating by 26Al is the dominant cause of planetesimal heating in any Solar system analogue scenario, thus validating previous works focussing only on this radioisotope. However, 60Fe can become the primary heating source in the case of high levels of supernova enrichment in massive star-forming regions. These diverging scenarios can affect the formation pathways, bulk volatile budget, and climate diversity of low-mass exoplanets.
      PubDate: Wed, 14 Feb 2024 00:00:00 GMT
      DOI: 10.1093/mnras/stae438
      Issue No: Vol. 528, No. 4 (2024)
       
  • A new test of gravity – II. Application of marked correlation functions
           to luminous red galaxy samples

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      Pages: 6631 - 6636
      Abstract: ABSTRACTWe apply the marked correlation function test proposed by Armijo et al. (Paper I) to samples of luminous red galaxies (LRGs) from the final data release of the Sloan Digital Sky Survey (SDSS) III. The test assigns a density-dependent mark to galaxies in the estimation of the projected marked correlation function. Two gravity models are compared: general relativity (GR) and $f(R)$ gravity. We build mock catalogues which, by construction, reproduce the measured galaxy number density and two-point correlation function of the LRG samples, using the halo occupation distribution model (HOD). A range of HOD models give acceptable fits to the observational constraints, and this uncertainty is fed through to the error in the predicted marked correlation functions. The uncertainty from the HOD modelling is comparable to the sample variance for the SDSS-III LRG samples. Our analysis shows that current galaxy catalogues are too small for the test to distinguish a popular $f(R)$ model from GR. However, upcoming surveys with a better measured galaxy number density and smaller errors on the two-point correlation function, or a better understanding of galaxy formation, may allow our method to distinguish between viable gravity models.
      PubDate: Tue, 13 Feb 2024 00:00:00 GMT
      DOI: 10.1093/mnras/stae449
      Issue No: Vol. 528, No. 4 (2024)
       
  • Classical Cepheid pulsation properties in the Rubin-LSST filters

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      Pages: 6637 - 6659
      Abstract: ABSTRACTHomogeneous multiwavelength observations of classical Cepheids from the forthcoming Rubin-LSST have the potential to significantly contribute to our understanding of the evolutionary and pulsation properties of these pulsating stars. Updated pulsation models for classical Cepheid stars have been computed under various assumptions about chemical compositions, including relatively low metallicity (Z = 0.004 with Y = 0.25 and Z = 0.008 with Y = 0.25), solar metallicity (Z = 0.02 with Y = 0.28), and supersolar metallicity environments (Z = 0.03 with Y = 0.28). From the predicted periods, intensity-weighted mean magnitudes, and colours, we have derived the first theoretical pulsation relations in the Rubin-LSST filters (ugrizy), including period–luminosity–colour, period–Wesenheit, and period–age–colour relations. We find that the coefficients of these relations are almost insensitive to the efficiency of superadiabatic convection but are significantly affected by the assumption of the mass–luminosity relation and the adopted chemical composition. Metal-dependent versions of these relations are also derived, representing valuable tools for individual distance determinations and correction for metallicity effects on the cosmic distance scale.
      PubDate: Tue, 13 Feb 2024 00:00:00 GMT
      DOI: 10.1093/mnras/stae450
      Issue No: Vol. 528, No. 4 (2024)
       
  • Long-term orbital evolution of dimorphos boulders and implications on the
           origin of meteorites

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      Pages: 6660 - 6665
      Abstract: ABSTRACTBy using recent observations of the Dydimos−Dimorphos system from the Hubble Space Telescope, 37 boulders with a size of 4 to 7 m ejected from the system during the impact with the DART spacecraft were identified. In this work, we studied the orbital evolution of a swarm of boulders with a similar size to that of the detected ones. By using recent estimates for the ejection velocity of the boulders, we numerically propagated the dynamics of the swarm for 20 kyr in the future. We found that the ejection velocities and the non-gravitational effects are not strong enough to change the secular evolution significantly. The minimum orbit intersection distance (MOID) with the Earth will be reached in about 2.5 kyr, but it will not fall below 0.02 au. On the contrary, the Mars MOID will be very small in four instances, two near 6 kyr and the other two near 15 kyr. Therefore, there may be a chance for them to impact Mars in the future. Given the rarefaction of the Martian atmosphere, we expect the boulders to arrive intact on the ground and excavate a small impact crater. The results presented here provide a further indication that some meteorites found on Earth originated in collisions of ∼100 m near-Earth asteroids with projectiles of ∼1 m in size.
      PubDate: Wed, 14 Feb 2024 00:00:00 GMT
      DOI: 10.1093/mnras/stae464
      Issue No: Vol. 528, No. 4 (2024)
       
  • Simulating image coaddition with the Nancy Grace Roman Space Telescope –
           II. Analysis of the simulated images and implications for weak lensing

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      Pages: 6680 - 6705
      Abstract: ABSTRACTOne challenge for applying current weak lensing analysis tools to the Nancy Grace Roman Space Telescope is that individual images will be undersampled. Our companion paper presented an initial application of Imcom – an algorithm that builds an optimal mapping from input to output pixels to reconstruct a fully sampled combined image – on the Roman image simulations. In this paper, we measure the output noise power spectra, identify the sources of the major features in the power spectra, and show that simple analytic models that ignore sampling effects underestimate the power spectra of the coadded noise images. We compute the moments of both idealized injected stars and fully simulated stars in the coadded images, and their one- and two-point statistics. We show that the idealized injected stars have root-mean-square ellipticity errors (1–6) × 10−4 per component depending on the band; the correlation functions are ≥2 orders of magnitude below requirements, indicating that the image combination step itself is using a small fraction of the overall Roman second moment error budget, although the fourth moments are larger and warrant further investigation. The stars in the simulated sky images, which include blending and chromaticity effects, have correlation functions near the requirement level (and below the requirement level in a wide-band image constructed by stacking all four filters). We evaluate the noise-induced biases in the ellipticities of injected stars, and explain the resulting trends with an analytical model. We conclude by enumerating the next steps in developing an image coaddition pipeline for Roman.
      PubDate: Tue, 16 Jan 2024 00:00:00 GMT
      DOI: 10.1093/mnras/stae177
      Issue No: Vol. 528, No. 4 (2024)
       
  • Can astronomical observations be used to constrain crucial chemical
           reactions' The methoxy case. SOLIS XVIII

    • Free pre-print version: Loading...

      Pages: 6706 - 6719
      Abstract: ABSTRACTTo understand the origin of interstellar molecules we rely on astrochemical models, the gas-phase networks of which contain ≥7000 reactions. However, just a tiny fraction of them have parameters derived in laboratory experiments. Theoretical quantum mechanical (QM) calculations can also provide this information. Unfortunately, sometimes theoretical predictions and experimental values disagree, as is the case for the paradigmatic reaction CH3OH + OH → CH3O + H2O. Both laboratory experiments and QM calculations found an unexpected increase in the rate coefficients with decreasing temperature. However, experimental and theoretical estimates of the rate coefficients diverge by up to two orders of magnitude at the low temperatures of interest in interstellar chemistry. This work aims to test whether astronomical observations can help untangle this confusing situation. To this end, we first carried out new QM calculations to derive the rate coefficients of the major destruction reaction of the methoxy radical, CH3O + H, and then we compared astronomical observations from the IRAM/NOEMA Large Programme SOLIS with astrochemical model predictions. Our new rate coefficient for the CH3O + H reaction is 5–10 times larger than that in the astrochemical data base KIDA in the 10–100 K range. When including the new methoxy destruction rate coefficients, the comparison between observations and model predictions favours the rate coefficients of the CH3OH + OH reaction from QM calculations. We conclude that QM calculations are an important alternative to laboratory experiments when it comes to the harsh conditions of interstellar objects and that astronomical observations can be used to constraint the rate coefficients of relevant reactions.
      PubDate: Tue, 20 Feb 2024 00:00:00 GMT
      DOI: 10.1093/mnras/stae232
      Issue No: Vol. 528, No. 4 (2024)
       
  • Viscous dissipation and dynamics in simulations of rotating, stratified
           plane-layer convection

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      Pages: 6720 - 6734
      Abstract: ABSTRACTConvection in stars and planets must be maintained against viscous and Ohmic dissipation. Here, we present the first systematic investigation of viscous dissipation in simulations of rotating, density-stratified plane layers of convection. Our simulations consider an anelastic ideal gas, and employ the open-source code Dedalus. We demonstrate that when the convection is sufficiently vigorous, the integrated dissipative heating tends towards a value that is independent of viscosity or thermal diffusivity, but depends on the imposed luminosity and the stratification. We show that knowledge of the dissipation provides a bound on the magnitude of the kinetic energy flux in the convection zone. In our non-rotating cases with simple flow fields, much of the dissipation occurs near the highest possible temperatures, and the kinetic energy flux approaches this bound. In the rotating cases, although the total integrated dissipation is similar, it is much more uniformly distributed (and locally balanced by work against the stratification), with a consequently smaller kinetic energy flux. The heat transport in our rotating simulations is in good agreement with results previously obtained for 3D Boussinesq convection, and approaches the predictions of diffusion-free theory.
      PubDate: Mon, 22 Jan 2024 00:00:00 GMT
      DOI: 10.1093/mnras/stae240
      Issue No: Vol. 528, No. 4 (2024)
       
  • Spectroscopic analysis of hot, massive stars in large spectroscopic
           surveys with de-idealized models

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      Pages: 6735 - 6750
      Abstract: ABSTRACTUpcoming large-scale spectroscopic surveys with e.g. WEAVE (William herschel telescope Enhanced Area Velocity Explorer) and 4MOST (4-metre Multi-Object Spectroscopic Telescope) will provide thousands of spectra of massive stars, which need to be analysed in an efficient and homogeneous way. Usually, studies of massive stars are limited to samples of a few hundred objects, which pushes current spectroscopic analysis tools to their limits because visual inspection is necessary to verify the spectroscopic fit. Often uncertainties are only estimated rather than derived and prior information cannot be incorporated without a Bayesian approach. In addition, uncertainties of stellar atmospheres and radiative transfer codes are not considered as a result of simplified, inaccurate, or incomplete/missing physics or, in short, idealized physical models. Here, we address the question of ‘How to compare an idealized model of complex objects to real data'’ with an empirical Bayesian approach and maximum a posteriori approximations. We focus on application to large-scale optical spectroscopic studies of complex astrophysical objects like stars. More specifically, we test and verify our methodology on samples of OB stars in 30 Doradus region of the Large Magellanic Clouds using a grid of fastwind model atmospheres. Our spectroscopic model de-idealization analysis pipeline takes advantage of the statistics that large samples provide by determining the model error to account for the idealized stellar atmosphere models, which are included into the error budget. The pipeline performs well over a wide parameter space and derives robust stellar parameters with representative uncertainties.
      PubDate: Tue, 30 Jan 2024 00:00:00 GMT
      DOI: 10.1093/mnras/stae298
      Issue No: Vol. 528, No. 4 (2024)
       
  • Effect of magnetically dependent heating on the behaviour of
           magnetoacoustic waves in coronal plasma with thermal misbalance

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      Pages: 6751 - 6760
      Abstract: ABSTRACTThe magnetic nature of coronal heating has been actively investigated within the framework of theoretical models and statistical analysis of observational data for decades. At present, a rather wide range of possible mechanisms has been proposed in the literature that requires additional verification. In this paper, we investigate the possibility of analysing the magnetic nature of coronal heating by means of magnetoacoustic (MA) waves propagating in coronal structures. To address this issue, we perform the analysis of fast and slow waves using a magnetic slab geometry. Applying the assumption of strong magnetic structuring, we derive the dispersion relation, which allows us to study the properties of MA waves. To analyse the dependence of phase velocity and wave decrement/increment on wavenumber, we numerically solved the obtained equations using the parameters corresponding to ‘warm’ coronal loop. It is shown that oscillations on the fundamental harmonic in a plasma with a weak magnetic field, where the effect of phase velocity dispersion is most pronounced, are best suited for diagnostics of magnetic heating using slow MA waves. In turn, the geometry remains the primary source for fast MA wave dispersion. Magnetic heating can either suppress or increase the damping of fast and slow MA waves. Moreover, the amplification of fast MA waves accompanied by damping of slow MA waves can be achieved. This issue is of interest in the context of the excitation of the decayless kink oscillations in the solar coronal loops.
      PubDate: Wed, 14 Feb 2024 00:00:00 GMT
      DOI: 10.1093/mnras/stae315
      Issue No: Vol. 528, No. 4 (2024)
       
  • Discovery and timing of pulsar J2016+3711 in supernova remnant
           CTB 87 with FAST

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      Pages: 6761 - 6767
      Abstract: ABSTRACTWe report on our discovery of the radio pulsar, PSR J2016+3711, in supernova remnant (SNR) CTB 87, with a ∼10.8σ significance of pulses, which confirms the compact nature of the X-ray point source in CTB 87. It is the first pulsar discovered in SNRs using Five-hundred-meter Aperture Spherical radio Telescope (FAST). Its integrated radio pulse profile can be well described by a single component, with a width at 50 per cent of the peak flux density of about 28.1○ and an effective width of about 32.2○. The mean flux density at 1.25 GHz is estimated to be about 15.5 $\mu$Jy. Combined with the non-detection of the radio pulse at lower frequencies, the radio spectral index of the pulsar is constrained to be ≲2.3. We also present the timing solution based on 28 follow-up FAST observations. Our results reveal a period of 50.81 ms, period derivative of 7.2 × 10−14 s s−1, and dispersion measure of 428 pc cm−3. The strength of the equatorial surface magnetic dipole magnetic field is inferred to be about 1.9 × 1012 G. Using the ephemeris obtained from the radio observations, we searched Fermi-LAT data for gamma-ray pulsations but detected no pulsed signal. We also searched for radio pulses with FAST towards the X-ray counterpart of the gamma-ray binary HESS J1832−093 proximate to SNR G22.7−00.2 but found no signal.
      PubDate: Mon, 05 Feb 2024 00:00:00 GMT
      DOI: 10.1093/mnras/stae351
      Issue No: Vol. 528, No. 4 (2024)
       
  • The ALMaQUEST Survey XIV: do radial molecular gas flows affect the
           star-forming ability of barred galaxies'

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      Pages: 6768 - 6785
      Abstract: ABSTRACTWe investigate whether barred galaxies are statistically more likely to harbour radial molecular gas flows and what effect those flows have on their global properties. Using 46 galaxies from the ALMA-MaNGA QUEnching and STar formation (ALMaQUEST) survey, we identify galaxies hosting optical bars using a combination of the morphological classifications in Galaxy Zoo 2 and HyperLEDA. In order to detect radial molecular gas flows, we employ full 3D kinematic modelling of the ALMaQUEST 12CO(1–0) data cubes. By combining our bar classifications with our radial bar-driven flow detections, we find that galaxies classed as barred are statistically more likely to host large-scale radial gas motions compared to their un-barred and edge-on galaxy counterparts. Moreover, the majority of barred galaxies require multicomponent surface brightness profiles in their best-fitting models, indicative of the presence of resonance systems. We find that galaxies classed as barred with radial bar-driven flows (‘barred + radial flow’ subset) have significantly suppressed global star-formation efficiencies compared to barred galaxies without radial bar-driven flows and galaxies in the other morphological sub-samples. Our ‘barred + radial flow’ subset galaxies also possess consistently centrally concentrated molecular gas distributions, with no indication of depleted gas mass fractions, suggesting that gas exhaustion is not the cause of their suppressed star formation. Furthermore, these objects have higher median gas mass surface densities in their central 1 kpc, implying that central gas enhancements do not fuel central starbursts in these objects. We propose that dynamical effects, such as shear caused by large-scale inflows of gas, act to gravitationally stabilize the inner gas reservoirs.
      PubDate: Tue, 06 Feb 2024 00:00:00 GMT
      DOI: 10.1093/mnras/stae377
      Issue No: Vol. 528, No. 4 (2024)
       
  • Accretion and magnetism on young eccentric binaries: DQ Tau and AK Sco

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      Pages: 6786 - 6806
      Abstract: ABSTRACTThe accretion and ejection of mass in pre-main-sequence (PMS) stars are key processes in stellar evolution as they shape the stellar angular momentum transport necessary for the stars’ stability. Magnetospheric accretion on to classical T Tauri stars and low-mass PMS stars has been widely studied in the single-star case. This process cannot be directly transferred to PMS binary systems, as tidal and gravitation effects, and/or accretion from a circumbinary disc (with variable separation of the components in the case of eccentric orbits) are in place. This work examines the accretion process of two PMS eccentric binaries, DQ Tau and AK Sco, using high-resolution spectropolarimetric time series. We investigate how magnetospheric accretion can be applied to these systems by studying the accretion-related emission lines and the magnetic field of each system. We discover that both systems are showing signs of magnetospheric accretion, despite their slightly different configurations, and the weak magnetic field of AK Sco. Furthermore, the magnetic topology of DQ Tau A shows a change relative to the previous orbital cycle studied: previously dominated by the poloidal component, it is now dominated by the toroidal component. We also report an increase of the component’s accretion and the absence of an accretion burst at the apastron, suggesting that the component’s magnetic variation might be the cause of the inter-cycle variations of the system’s accretion. We conclude on the presence of magnetospheric accretion for both systems, together with gravitational effects, especially for AK Sco, composed of more massive components.
      PubDate: Tue, 06 Feb 2024 00:00:00 GMT
      DOI: 10.1093/mnras/stae383
      Issue No: Vol. 528, No. 4 (2024)
       
  • Transient quasi-periodic oscillations in the gamma-ray light curves of
           bright blazars

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      Pages: 6807 - 6822
      Abstract: ABSTRACTTransient quasi-periodic oscillations (QPOs) are extremely interesting observational phenomena. However, the precise physical mechanisms leading to their generation are still hotly debated. We performed a systematic search for transient QPO signals using Weighted Wavelet Z-transforms on the gamma-ray light curves of 134 bright blazars with peak flux exceeding 1 × 10−6 ph cm−2 s−1 as monitored by Fermi-LAT. Artificial light curves were generated from the power spectral density and probability distribution functions of the original light curves to assess the significance level of transient QPO. We discuss several physical mechanisms that produce transient QPOs, with the helical jet model providing the best explanation. This study identified four new transient QPO events. Interestingly, repetitive transient QPOs are observed in PKS 0537-441, and nested transient QPOs are detected in PKS 1424−41. Additionally, we find that transient QPOs tend to occur in the flare state of the blazar. Finally, we estimate the incidence of transient QPO events to be only about 3 per cent.
      PubDate: Thu, 08 Feb 2024 00:00:00 GMT
      DOI: 10.1093/mnras/stae416
      Issue No: Vol. 528, No. 4 (2024)
       
  • The optical intra-day variability of BL laceratae object
           2200 + 420

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      Pages: 6823 - 6835
      Abstract: ABSTRACTWe observed the blazar 2200 + 420 in the I, R, and V bands using the 1.0 m telescope at Weihai Observatory of Shandong University on eight nights in October 2022 and obtained over 3800 data points. Using the F-test and ANOVA test, we analysed the light curves and found intra-day (IDV) variability every night. We found that all variability amplitudes (Amp) are over 10 per cent, except for 2022 October 22, with four nights having amplitudes above 20 per cent and the maximum amplitude reaching over 42 per cent. Additionally, we discovered a minimal variability time-scale of 24.6 min and a bluer-when-brighter (BWB) trend on intra-day for this object. No significant time lag between different bands was detected during the eight nights of observation. Based on the shortest variability time-scale and a model assuming the variations arise close to the central black hole that are adverted into the jet, we estimated the upper limits of the black hole mass to be MBH = 8.6 × 107 M⊙. The BWB trend on intra-day supports the shock-in-jet model, which can also explain the IDV of blazars.
      PubDate: Fri, 09 Feb 2024 00:00:00 GMT
      DOI: 10.1093/mnras/stae422
      Issue No: Vol. 528, No. 4 (2024)
       
  • Doppler signature of a possible termination shock in an off-limb solar
           flare

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      Pages: 6836 - 6844
      Abstract: ABSTRACTWe report striking Doppler velocity gradients observed during the well-observed 2017 September 10 solar flare, and argue that they are consistent with the presence of an above-the-looptop termination shock beneath the flare current sheet. Observations from the Hinode Extreme-ultraviolet Imaging Spectrometer measure plasma sheet Doppler shifts up to 35 km s−1 during the late-phase of the event. By comparing these line-of-sight flows with plane-of-sky (POS) measurements, we calculate total velocity downflows of 200+ km s−1, orientated ≈6–10° out of the POS. The observed velocities drop rapidly at the base of the hot plasma sheet seen in extreme ultraviolet, consistent with simulated velocity profiles predicted by our 2.5D magnetohydrodynamics model that features a termination shock at the same location. Finally, the striking velocity deceleration aligns spatially with the suppression of Fe xxiv non-thermal velocities, and a 35–50 keV hard X-ray looptop source observed by the Reuven Ramaty High Energy Solar Spectroscopic Imager. Together, these observations are consistent with the presence of a possible termination shock within the X8.2-class solar flare.
      PubDate: Fri, 09 Feb 2024 00:00:00 GMT
      DOI: 10.1093/mnras/stae430
      Issue No: Vol. 528, No. 4 (2024)
       
  • Probing the small-scale structure of the intergalactic medium with
           ESPRESSO: spectroscopy of the lensed QSO UM673

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      Pages: 6845 - 6860
      Abstract: ABSTRACTThe gravitationally lensed quasar J014516.6-094517 at z = 2.719 has been observed with the ESPRESSO instrument at the ESO VLT to obtain high-fidelity spectra of the two images A and B with a resolving power R = 70 000. At the redshifts under investigation (2.1 ≲ z ≲ 2.7), the Lyman forests along the two sightlines are separated by sub-kiloparsec physical distances and exhibit a strong correlation. We find that the two forests are indistinguishable at the present level of signal-to-noise ratio and do not show any global velocity shift, with the cross-correlation peaking at Δv = 12 ± 48 $\rm m~s^{-1}$. The distribution of the difference in velocity of individual Ly α features is compatible with a null average and a mean absolute deviation of 930 $\rm m~s^{-1}$. Significant differences in NH i column density are not detected, putting a limit to the RMS fluctuation in the baryon density on ≲1 proper kpc scales of Δρ/ρ ≲ 3 per cent. On the other hand, metal lines show significant differences both in velocity structure and in column density. A toy model shows that the difference in velocity of the metal features between the two sightlines is compatible with the motions of the baryonic component associated with dark matter haloes of typical mass M ≃ 2 × 1010 M⊙, also compatible with the observed incidence of the metal systems. The present observations confirm the feasibility of the Sandage test of the cosmic redshift drift with high-fidelity spectroscopy of the Lyman forest of distant, bright quasars, but also provide an element of caution about the intrinsic noise associated with the usage of metal features for the same purpose.
      PubDate: Mon, 12 Feb 2024 00:00:00 GMT
      DOI: 10.1093/mnras/stae432
      Issue No: Vol. 528, No. 4 (2024)
       
  • Reassessing the constraints from SH0ES extragalactic Cepheid amplitudes on
           systematic blending bias

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      Pages: 6861 - 6880
      Abstract: ABSTRACTThe SH0ES collaboration Hubble constant determination is in a ∼5σ difference with the Planck value, known as the Hubble tension. The accuracy of the Hubble constant measured with extragalactic Cepheids depends on robust stellar-crowding background estimation. Riess et al. (R20) compared the light-curve amplitudes of extragalactic and MW Cepheids to constrain an unaccounted systematic blending bias, $\gamma =-0.029\pm 0.037\, \rm {mag}$, which cannot explain the required, $\gamma =0.24\pm 0.05\, \rm {mag}$, to resolve the Hubble tension. Further checks by Riess et al. demonstrate that a possible blending is not likely related to the size of the crowding correction. We repeat the R20 analysis, with the following main differences: (1) we limit the extragalactic and MW Cepheids comparison to periods $P\lesssim 50\, \rm {d}$, since the number of MW Cepheids with longer periods is minimal; (2) we use publicly available data to recalibrate amplitude ratios of MW Cepheids in standard passbands; (3) we remeasure the amplitudes of Cepheids in NGC 5584 and NGC 4258 in two Hubble Space Telescope filters (F555W and F350LP) to improve the empirical constraint on their amplitude ratio A555/A350. We show that the filter transformations introduce an ${\approx }0.04\, \rm {mag}$ uncertainty in determining γ, not included by R20. While our final estimate, $\gamma =0.013\pm 0.057\, \rm {mag}$, is consistent with the value derived by R20 and is consistent with no bias, the error is somewhat larger, and the best-fitting value is shifted by ${\approx }0.04\, \rm {mag}$ and closer to zero. Future observations, especially with JWST, would allow better calibration of γ.
      PubDate: Wed, 14 Feb 2024 00:00:00 GMT
      DOI: 10.1093/mnras/stae451
      Issue No: Vol. 528, No. 4 (2024)
       
  • Structure and composition of Jupiter, Saturn, Uranus, and Neptune under
           different constraints and distortion due to rotation

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      Pages: 6881 - 6894
      Abstract: ABSTRACTThe radii of planets serve as significant constraints for their internal structure. Despite the complexity of planetary internal structure compared to stars, substantial advancements have been made in this field. The most critical uncertainties stem from the chemical composition and equation of state of planetary material. Using the MESA code, we construct rotating and non-rotating interior models for Jupiter and Saturn and sought to align these models to the observed radii. Rotation exerts a significant influence on their structures, distorting planetary, and stellar structures in distinct ways. Regarding gas planets’ structure, two pivotal uncertain parameters depend on a possible separation between hydrogen and helium in the protosolar disc gas due to unequal evaporation between these two gases. In an extreme scenario where only hydrogen is lost and no heavy elements or helium are lost, Jupiter and Saturn would have a core mass of zero. However, this approach fails to yield a solution for Uranus and Neptune. Instead, our models indicate that hydrogen and helium were likely lost together during the protosolar disc phase, resulting in core masses of approximately 40, 25, 14, and 12 M⊕ for Jupiter, Saturn, Neptune, and Uranus, respectively. These findings are highly compatible with the observed mass–radius relationship of exoplanets, as well as the seismic and Juno data for Jupiter’s near-surface temperature.
      PubDate: Wed, 14 Feb 2024 00:00:00 GMT
      DOI: 10.1093/mnras/stae476
      Issue No: Vol. 528, No. 4 (2024)
       
  • On the origin of outward migration of Population III stars

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      Pages: 6895 - 6914
      Abstract: ABSTRACTOutward migration of massive binary stars or black holes in their circumbinary disc is often observed in simulations and it is key to the formation of wide black hole binaries. Using numerical simulations of Population III (Pop III) star formation, we study the angular momentum of Pop III binaries and the torques between stars and gas discs to understand the origin of outward migration and high ellipticity. The outward migration of protostars is produced by gravitational torques exerted on them by their circumstellar minidiscs. The minidiscs, on the other hand, migrate outward mainly by gaining angular momentum by accreting gas from the circumbinary disc. The angular momentum transfer is most efficient for rapidly accreting equal-mass binaries, and weaker when the secondary mass is small or the massive companion evaporates the gas disc via radiative feedback. We conclude that outward migration and the formation of wide equal-mass massive binaries is common in metal-free/metal-poor star formation, mainly driven by their large accretion rates. We expect that the lower gas temperature and accretion rates in metal-enriched circumstellar discs would lead more often to inward migration and closer binary separations. We also observe inward migration for smaller mass Pop III protostars/fragments, leading to the rapid merging of sink particles and likely the formation of close binary black holes that, however, reach separations below the resolution of our simulations. We discuss the implications that Pop III separations and ellipticity may have on the interpretation that gravitational wave signals from merging intermediate-mass black holes come from Pop III remnants.
      PubDate: Mon, 19 Feb 2024 00:00:00 GMT
      DOI: 10.1093/mnras/stae518
      Issue No: Vol. 528, No. 4 (2024)
       
  • A post-merger enhancement only in star-forming Type 2 Seyfert galaxies:
           the deep learning view

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      Pages: 6915 - 6933
      Abstract: ABSTRACTSupermassive black holes require a reservoir of cold gas at the centre of their host galaxy in order to accrete and shine as active galactic nuclei (AGN). Major mergers have the ability to drive gas rapidly inwards, but observations trying to link mergers with AGN have found mixed results due to the difficulty of consistently identifying galaxy mergers in surveys. This study applies deep learning to this problem, using convolutional neural networks trained to identify simulated post-merger galaxies from survey-realistic imaging. This provides a fast and repeatable alternative to human visual inspection. Using this tool, we examine a sample of ∼8500 Seyfert 2 galaxies ($L[\mathrm{O\, {\small III}}] \sim 10^{38.5 - 42}$ erg s−1) at z < 0.3 in the Sloan Digital Sky Survey and find a merger fraction of $2.19_{-0.17}^{+0.21}$ per cent compared with inactive control galaxies, in which we find a merger fraction of $2.96_{-0.20}^{+0.26}$ per cent, indicating an overall lack of mergers among AGN hosts compared with controls. However, matching the controls to the AGN hosts in stellar mass and star formation rate reveals that AGN hosts in the star-forming blue cloud exhibit a ∼2 × merger enhancement over controls, while those in the quiescent red sequence have significantly lower relative merger fractions, leading to the observed overall deficit due to the differing M*–SFR distributions. We conclude that while mergers are not the dominant trigger of all low-luminosity, obscured AGN activity in the nearby Universe, they are more important to AGN fuelling in galaxies with higher cold gas mass fractions as traced through star formation.
      PubDate: Thu, 22 Feb 2024 00:00:00 GMT
      DOI: 10.1093/mnras/stae183
      Issue No: Vol. 528, No. 4 (2024)
       
  • On the effects of photoionization feedback on second-generation star
           formation in globular clusters of different masses

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      Pages: 5477 - 5486
      Abstract: ABSTRACTWe simulate the formation of second-generation (SG) stars in young clusters with masses of 105 and $10^6\, \mathrm{M}_{\odot }$ within $30\!-\!100\, \mathrm{Myr}$ after the formation of clusters. We assume the clusters move through a uniform interstellar medium with gas densities of 10−24 and $10^{-23}\, \mathrm{g\, cm}^{-3}$ and consider the stellar winds from asymptotic giant branch (AGB) stars, gas accretion on to the cluster, ram pressure, star formation, and photoionization feedback of our stellar systems including binary stars. We find that SG stars can be formed only within the $10^6\, \mathrm{M}_{\odot }$ cluster in the high-density simulation, where the cluster can accrete sufficient pristine gas from their surrounding medium, leading to efficient cooling required for the ignition of SG formation and sufficient dilution of the AGB ejecta. Hence, our results indicate that a denser environment is another requirement for the AGB scenario to explain the presence of multiple populations in globular clusters. On the other hand, the ionizing feedback becomes effective in heating the gas in our low-density simulations. As a result, the clusters cannot accumulate a considerable amount of pristine gas at their centre. The gas mass within the clusters in these simulations is similar to that in young massive clusters (YMCs). Hence, our studies can provide a possible reason for the lack of gas, star formation, and SG stars in YMCs. Our results indicate that the ionizing stellar feedback is not a severe problem for SG formation; rather, it can help the AGB scenario to account for some observables.
      PubDate: Tue, 12 Dec 2023 00:00:00 GMT
      DOI: 10.1093/mnras/stad3771
      Issue No: Vol. 528, No. 4 (2023)
       
  • On the similarity of rotational motion of dust particles in the inner
           atmosphere of comets

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      Pages: 5723 - 5729
      Abstract: ABSTRACTIn situ measurements of individual dust grain parameters in the immediate vicinity of a cometary nucleus are being carried by the Rosetta spacecraft at comet 67P/Churyumov–Gerasimenko. For interpretation of these observational data, a model of dust grain motion as realistic as possible is requested. In particular, the results of Stardust mission and analysis of samples of interplanetary dust have shown that these particles are highly non-spherical. In many cases precise simulations of non-spherical grain’s dynamics is either impossible or computationally too expensive. In such situation it is proposed to use available experimental or numerical data obtained for other conditions and rescale them considering similarity of the physical process. In the present paper we focus on the derivation of scaling laws of rotational motion applicable for any shape of particles. We use a set of universal, dimensionless parameters characterizing the dust motion in the inner cometary coma. The scaling relations for translational and rotational motion of dust grains in a cometary environment are proposed. The scaled values are compared with numerically computed ones in our previous works.
      PubDate: Tue, 12 Sep 2023 00:00:00 GMT
      DOI: 10.1093/mnras/stad2665
      Issue No: Vol. 528, No. 4 (2023)
       
  • Characterization of Herschel-selected strong lens candidates through HST
           and sub-mm/mm observations

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      Pages: 6222 - 6279
      Abstract: ABSTRACTWe have carried out Hubble Space Telescope (HST) snapshot observations at 1.1 μm of 281 candidate strongly lensed galaxies identified in the wide-area extragalactic surveys conducted with the Herschel Space Observatory. Our candidates comprise systems with flux densities at $500\, \mu$m, S500 ≥ 80 mJy. We model and subtract the surface brightness distribution for 130 systems, where we identify a candidate for the foreground lens candidate. After combining visual inspection, archival high-resolution observations, and lens subtraction, we divide the systems into different classes according to their lensing likelihood. We confirm 65 systems to be lensed. Of these, 30 are new discoveries. We successfully perform lens modelling and source reconstruction on 23 systems, where the foreground lenses are isolated galaxies and the background sources are detected in the HST images. All the systems are successfully modelled as a singular isothermal ellipsoid. The Einstein radii of the lenses and the magnifications of the background sources are consistent with previous studies. However, the background source circularized radii (between 0.34 and 1.30 kpc) are ∼3 times smaller than the ones measured in the sub-millimetre/millimetre for a similarly selected and partially overlapping sample. We compare our lenses with those in the Sloan Lens Advanced Camera for Surveys (ACS) Survey confirming that our lens-independent selection is more effective at picking up fainter and diffuse galaxies and group lenses. This sample represents the first step towards characterizing the near-infrared properties and stellar masses of the gravitationally lensed dusty star-forming galaxies.
      PubDate: Fri, 03 Nov 2023 00:00:00 GMT
      DOI: 10.1093/mnras/stad3381
      Issue No: Vol. 528, No. 4 (2023)
       
  • An Overview of Sunspot Observations in the Early Maunder Minimum:
           1645–1659

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      Pages: 6280 - 6291
      Abstract: AbstractWithin four centuries of sunspot observations, the Maunder Minimum (MM) in 1645–1715 has been considered a unique grand minimum with weak solar cycles in group numbers of sunspots and hemispheric asymmetry in sunspot positions. However, the early part of the MM (1645–1659) is poorly understood in terms of its source records and has accommodated diverse reconstructions of the contemporaneous group number. This study identified their source records, classidied them in three different categories (datable observations, general descriptions, and misinterpreted records), and revised their data. On this basis, we estimated the yearly mean group number using the brightest star method, derived the active day fraction (ADF), reconstructed the sunspot number based on ADF, and compared them with proxy reconstructions from the tree-ring data sets. Our results revised the solar activity in the early MM downward in yearly mean group numbers using the brightest star method and upward in the active day fraction and sunspot number estimates. Our results are consistent with the proxy reconstruction for 1645–1654 and show more realistic values for 1657–1659 (against the unphysical negative sunspot number). These records have paid little attention to sunspot positions, except for Hevelius' report on a sunspot group in the northern solar hemisphere in 1652 April. Therefore, slight caveats are required to discuss if the sunspot positions are located purely in the southern solar hemisphere throughout the MM.
      PubDate: Wed, 20 Dec 2023 00:00:00 GMT
      DOI: 10.1093/mnras/stad3922
      Issue No: Vol. 528, No. 4 (2023)
       
  • Sandwiched planet formation: restricting the mass of a middle planet

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      Pages: 6538 - 6549
      Abstract: ABSTRACTWe conduct gas and dust hydrodynamical simulations of protoplanetary discs with one and two embedded planets to determine the impact that a second planet located further out in the disc has on the potential for subsequent planet formation in the region locally exterior to the inner planet. We show how the presence of a second planet has a strong influence on the collection of solid material near the inner planet, particularly when the outer planet is massive enough to generate a maximum in the disc’s pressure profile. This effect in general acts to reduce the amount of material that can collect in a pressure bump generated by the inner planet. When viewing the inner pressure bump as a location for potential subsequent planet formation of a third planet, we therefore expect that the mass of such a planet will be smaller than it would be in the case without the outer planet, resulting in a small planet being sandwiched between its neighbours – this is in contrast to the expected trend of increasing planet mass with radial distance from the host star. We show that several planetary systems have been observed that do not show this trend but instead have a smaller planet sandwiched in between two more massive planets. We present the idea that such an architecture could be the result of the subsequent formation of a middle planet after its two neighbours formed at some earlier stage.
      PubDate: Tue, 31 Oct 2023 00:00:00 GMT
      DOI: 10.1093/mnras/stad3163
      Issue No: Vol. 528, No. 4 (2023)
       
  • The Lyman-α forest catalogue from the Dark Energy Spectroscopic
           Instrument Early Data Release

    • Free pre-print version: Loading...

      Pages: 6666 - 6679
      Abstract: ABSTRACTWe present and validate the catalogue of Lyman-α forest fluctuations for 3D analyses using the Early Data Release (EDR) from the Dark Energy Spectroscopic Instrument (DESI) survey. We used 88 511 quasars collected from DESI Survey Validation (SV) data and the first two months of the main survey (M2). We present several improvements to the method used to extract the Lyman-α absorption fluctuations performed in previous analyses from the Sloan Digital Sky Survey (SDSS). In particular, we modify the weighting scheme and show that it can improve the precision of the correlation function measurement by more than 20 per cent. This catalogue can be downloaded from https://data.desi.lbl.gov/public/edr/vac/edr/lya/fuji/v0.3, and it will be used in the near future for the first DESI measurements of the 3D correlations in the Lyman-α forest.
      PubDate: Thu, 07 Dec 2023 00:00:00 GMT
      DOI: 10.1093/mnras/stad3781
      Issue No: Vol. 528, No. 4 (2023)
       
 
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