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- A question of personalities: evolution of viscous and wind-driven
protoplanetary discs in the presence of dead zones-
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Pages: 1211 - 1232
Abstract: ABSTRACTWhether the angular momentum of protoplanetary discs is redistributed by viscosity or extracted by magnetized winds is a long-standing question. Demographic indicators, such as gas disc sizes and stellar accretion rates, have been proposed as ways of distinguishing between these two mechanisms. In this paper, we implement one-dimensional gas simulations to study the evolution of ‘hybrid’ protoplanetary discs simultaneously driven by viscosity and magnetized winds, with dead zones present. We explore how the variations of disc properties, including initial disc sizes, dead zone sizes, and angular momentum transport efficiency, affect stellar accretion rates, disc surface density profiles, disc sizes, disc lifetimes, and cumulative mass-loss by different processes. Our models show that the expansion of the gas disc size can be sustained when the majority of angular momentum is removed by the magnetized wind for individual protoplanetary discs. However, when we can only observe discs via demographic screenshots, the variation of disc sizes with time is possibly diminished by the disc ‘personalities’, by which we mean the variations of initial disc properties among different discs. Our ‘hybrid’ models re-assess association of the two demographic indicators with mechanisms responsible for angular momentum transport and suggest that additional diagnostics are required to assist the differentiation.
PubDate: Thu, 18 Jul 2024 00:00:00 GMT
DOI: 10.1093/mnras/stae1748
Issue No: Vol. 533, No. 2 (2024)
- Underluminous tidal disruption events
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Pages: 1233 - 1250
Abstract: ABSTRACTWe have evidence of X-ray flares in several galaxies consistent with a star being tidally disrupted by a supermassive black hole (MBH). If the star starts on a nearly parabolic orbit relative to the MBH, one can derive that the fallback rate follows a $t^{-5/3}$ decay. Depending on the penetration factor, β, a star will be torn apart differently, and relativistic effects play a role. We have modified the standard version of the smoothed-particle hydrodynamics (SPH) code Gadget to include a relativistic treatment of the gravitational forces between the gas particles of a main-sequence (MS) star and a MBH. We include non-spinning post-Newtonian corrections to incorporate the periapsis shift and the spin-orbit coupling up to next-to-lowest order. We find that tidal disruptions around MBHs in the relativistic cases are underluminous for values starting at $\beta \gtrapprox 2.25$, i.e. the fallback curves produced in the relativistic cases are progressively lower compared to the Newtonian simulations as the penetration parameter increases. While the Newtonian cases display a total disruption, we find that all relativistic counterparts feature a survival core for penetration factors going to values as high as 12.05. We perform a additional dynamical numerical study that shows that the geodesics of the elements in the star converge at periapsis. We confirm these findings with an analytical study of the geodesic separation equation. The luminosity of TDEs must be lower than predicted theoretically due to the fact that the star will partially survive when relativistic effects are taken into account. A survival core should consistently emerge from any TDE with $\beta \gtrapprox 2.25$.
PubDate: Mon, 22 Jul 2024 00:00:00 GMT
DOI: 10.1093/mnras/stae1756
Issue No: Vol. 533, No. 2 (2024)
- Nebular nitrogen line emission in stripped-envelope supernovae – a new
progenitor mass diagnostic-
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Pages: 1251 - 1280
Abstract: ABSTRACTNitrogen is produced by CNO-cycling in massive stars, and can be ejected in significant amounts in supernova explosions. While in H-rich SNe, its [N ii] 6548, 6583 emission becomes obscured by strong H$\alpha$, in explosions of He stars, this nitrogen emission becomes more visible. We here explore the formation of this line, using the sumo code to compute spectra for a grid of 1D models with parametrized mixing informed from new 2D simulations. Because the mass fraction of nitrogen in the ejecta decreases with larger He-core masses, as more of the He/N zone gets processed by shell helium burning and is lost to winds, the [N ii] luminosity relative to the overall optical flux probes the He-core mass. By comparing to large samples of data, we find that low-mass He cores ($M_{\rm preSN}\lesssim \ 3\ \mathrm{ M}_\odot$) are exclusively associated with Type IIb SNe, with the exception of Type Ib SN 2007Y. Seeing no strong nitrogen emission in other Type Ib SNe, the implication is either an origin from low-mass stars with the He/N layer (but not the He/C) layer peeled away, or from higher mass He cores. We also see no clear nitrogen emission in Type Ic SNe. We discuss the diagnostic potential of this new line metric, and also dependencies on mass-loss rate and metallicity.
PubDate: Fri, 26 Jul 2024 00:00:00 GMT
DOI: 10.1093/mnras/stae1811
Issue No: Vol. 533, No. 2 (2024)
- First deep X-ray observations of the Fermi-detected steep-spectrum source
and radio-loud NLS1 galaxy 3C 286-
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Pages: 1281 - 1289
Abstract: ABSTRACTA well-known calibrator source in radio astronomy, 3C 286 ($z=0.85$), is a compact steep-spectrum (CSS) radio source and spectroscopically classified as a narrow-line Seyfert 1 (NLS1) galaxy. It is also known for its damped Ly $\alpha$ system from an intervening galaxy at $z=0.692$ detected in both ultraviolet (UV) and radio spectra. In addition, despite being a misaligned active galactic nuclei (AGN), 3C 286 is also detected in $\gamma$-rays by Fermi. Thus, this unique object combines the characteristics of CSS sources, NLS1 galaxies, and $\gamma$-ray emitters with misaligned jets, providing an excellent laboratory for extending our knowledge of AGN disc–jet coupling. Despite its significance, 3C 286 has been rarely observed in X-rays. In this study, we present our deep XMM–Newton and Chandra observations of 3C 286. The results reveal that the X-ray spectrum can be well-described by models including an intervening absorber with redshift and column density consistent with previous UV and radio observations. The most important finding is that the spectrum cannot be described by a single power law, but a soft excess is required which is parametrized by a blackbody. Furthermore, we find evidence suggesting the presence of off-nuclear X-ray emission at a radius that corresponds to the location of the radio lobes. While further theoretical work is still needed, our findings offer new clues to understand the specific mechanism for $\gamma$-ray emission from this unique object.
PubDate: Fri, 26 Jul 2024 00:00:00 GMT
DOI: 10.1093/mnras/stae1827
Issue No: Vol. 533, No. 2 (2024)
- The impact of stellar metallicity on rotation and activity evolution in
the Kepler field using gyro-kinematic ages-
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Pages: 1290 - 1299
Abstract: ABSTRACTIn recent years, there has been a push to understand how chemical composition affects the magnetic activity levels of main sequence low-mass stars. Results indicate that more metal-rich stars are more magnetically active for a given stellar mass and rotation period. This metallicity dependence has implications for how the rotation periods and activity levels of low-mass stars evolve over their lifetimes. Numerical modelling suggests that at late ages more metal-rich stars should be rotating more slowly and be more magnetically active. In this work, we study the rotation and activity evolution of low-mass stars using a sample of Kepler field stars. We use the gyro-kinematic age dating technique to estimate ages for our sample and use the photometric activity index as our proxy for magnetic activity. We find clear evidence that, at late ages, more metal-rich stars have spun down to slower rotation in agreement with the theoretical modelling. However, further investigation is required to definitively determine whether the magnetic activity evolution occurs in a metallicity dependent way.
PubDate: Tue, 30 Jul 2024 00:00:00 GMT
DOI: 10.1093/mnras/stae1828
Issue No: Vol. 533, No. 2 (2024)
- The MAGPI survey: evidence against the bulge–halo conspiracy
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Pages: 1300 - 1320
Abstract: ABSTRACTStudies of the internal mass structure of galaxies have observed a ‘conspiracy’ between the dark matter and stellar components, with total (stars$+$dark) density profiles showing remarkable regularity and low intrinsic scatter across various samples of galaxies at different redshifts. Such homogeneity suggests the dark and stellar components must somehow compensate for each other in order to produce such regular mass structures. We test the conspiracy using a sample of 22 galaxies from the ‘Middle Ages Galaxy Properties with Integral field spectroscopy’ Survey that targets massive galaxies at $z \sim 0.3$. We use resolved, 2D stellar kinematics with the Schwarzschild orbit-based modelling technique to recover intrinsic mass structures, shapes, and dark matter fractions. This work is the first implementation of the Schwarzschild modelling method on a sample of galaxies at a cosmologically significant redshift. We find that the variability of structure for combined mass (baryonic and dark) density profiles is greater than that of the stellar components alone. Furthermore, we find no significant correlation between enclosed dark matter fractions at the half-light radius and the stellar mass density structure. Rather, the total density profile slope, $\gamma _{\mathrm{tot}}$, strongly correlates with the dark matter fraction within the half-light radius, as $\gamma _{\mathrm{tot}} = (1.3 \pm 0.2) f_{\mathrm{DM}} - (2.44 \pm 0.04)$. Our results refute the bulge–halo conspiracy and suggest that stochastic processes dominate in the assembly of structure for massive galaxies.
PubDate: Sat, 10 Aug 2024 00:00:00 GMT
DOI: 10.1093/mnras/stae1836
Issue No: Vol. 533, No. 2 (2024)
- Signatures of gas flows – I. Connecting the kinematics of the H i
circumgalactic medium to galaxy rotation-
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Pages: 1321 - 1340
Abstract: ABSTRACTThe circumgalactic medium (CGM) hosts many physical processes with different kinematic signatures that affect galaxy evolution. We address the CGM–galaxy kinematic connection by quantifying the fraction of H i that is aligned with galaxy rotation with the equivalent width co-rotation fraction, $f_{\rm EWcorot}$. Using 70 quasar sightlines having Hubble Space Telescope/Cosmic Origins Spectrograph H i absorption (${12\lt \log (N(\rm{{\rm H}\,{\small I}})/{\rm cm}^{-2})\lt 20}$) within $5R_{\rm vir}$ of $z\lt 0.6$ galaxies we find that $f_{\rm EWcorot}$ increases with increasing H i column density. $f_{\rm EWcorot}$ is flat at $\sim 0.6$ within $R_{\rm vir}$ and decreases beyond $R_{\rm vir}$ to $f_{\rm EWcorot}$$\sim 0.35$. $f_{\rm EWcorot}$ also has a flat distribution with azimuthal and inclination angles within $R_{\rm vir}$, but decreases by a factor of two outside of $R_{\rm vir}$ for minor axis gas and by a factor of 2 for edge-on galaxies. Inside $R_{\rm vir}$, co-rotation dominated H i is located within $\sim 20$ deg of the major and minor axes. We surprisingly find equal amounts of H i absorption consistent with co-rotation along both major and minor axes within $R_{\rm vir}$. However, this co-rotation disappears along the minor axis beyond $R_{\rm vir}$, suggesting that if this gas is from outflows, then it is bound to galaxies. $f_{\rm EWcorot}$ is constant over two decades of halo mass, with no decrease for log(M$_{\rm h}/{\rm M}_{\odot })\gt 12$ as expected from simulations. Our results suggest that co-rotating gas flows are best found by searching for higher column density gas within $R_{\rm vir}$ and near the major and minor axes.
PubDate: Wed, 31 Jul 2024 00:00:00 GMT
DOI: 10.1093/mnras/stae1843
Issue No: Vol. 533, No. 2 (2024)
- Orbital motion of NGC 6166 (3C 338) and its impact on the jet morphology
at kiloparsec scales-
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Pages: 1341 - 1366
Abstract: ABSTRACTIn the central region of the galaxy cluster, Abell 2199 (A 2199) resides the cD galaxy NGC 6166, which spatially coincides with the 3C 338 radio source. Lobes, jets, and a more detached southern structure (similar to a jet labelled as ridge) are seen at kiloparsec-scale images of 3C 338. This unusual radio morphology has led to the proposition of different hypotheses about its physical origin in the literature. In this work, we study the feasibility of a dynamical scenario where NGC 6166 moves around the X-ray inferred centre of A 2199 from the point of view of three-dimensional hydrodynamic simulations. The physical characteristics of the intracluster medium in which the jet propagates are constrained to those derived from X-ray observations in the vicinity of NGC 6166. Possible orbits for the jet inlet region are derived from the estimated radial velocity of NGC 6166, while the jet parameters are constrained by parsec-scale interferometric radio observations and the estimated jet power of 3C 338 obtained from radio and X-ray data. Our results show that the hypothesis of NGC 6166 has been moving around the centre of A 2199 during the last tens of million of years is compatible with the general radio morphology of 3C 338. Furthermore, the proposed dynamic scenario for the motion of NGC 6166 may be linked to gravitational perturbations induced by the passage of a sub-cluster of galaxies hundreds of millions of years ago.
PubDate: Wed, 31 Jul 2024 00:00:00 GMT
DOI: 10.1093/mnras/stae1846
Issue No: Vol. 533, No. 2 (2024)
- Excitation of CO molecules in diffuse gas over cosmic history
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Pages: 1367 - 1393
Abstract: ABSTRACTWe studied the physical conditions in the local interstellar medium (ISM) and at high redshift by fitting observed column densities of CO and H2 rotational levels and C i fine-structure levels using photodissociation models calculated with the Meudon PDR code. We analysed CO absorption systems in 28 sight lines in the local ISM and seven damped Lyman-α absorption systems at high redshift, covering $N({\rm H_2})=10^{19}\!-\!10^{21.5}\,{\rm cm}^{-2}$ and $N({\rm CO})=10^{13}\!-\!10^{18}\,{\rm cm}^{-2}$. We constructed a method to accurately calculate CO excitation, incorporating the effects of photon trapping. Our findings indicate that in the local ISM, CO excitation is primarily driven by collisions and excitation due to the CMB radiation. We demonstrated that an increase in CO excitation observed near $N({\rm CO})\simeq 10^{15}~{\rm cm^{-2}}$, is attributed to an increase in gas densities from ${\simeq}100\,{\rm cm}^{-3}$ to ${\simeq}300\!-\!1000\,{\rm cm}^{-3}$. CO absorption systems in the local ISM are characterized by a gas number density of about 10–1000 cm−3, a kinetic temperature of 10–100 K, and an intensity of external UV field ranging from 0.1 to 10 units of Mathis field. Compared to the average gas probed by C i absorption, the gas detected in CO is denser and colder, while the external UV field remains nearly constant. We observed a negative correlation between the kinetic temperature and both N(CO) and N(H2), with power-law slopes of $-0.21\pm 0.02$ and $-0.65\pm 0.05$, respectively. At the same time, the gas number density exhibits a positive correlation with N(CO) and N(H2) with slopes of $0.38\pm 0.02$ and $1.15\pm 0.05$, respectively.
PubDate: Fri, 09 Aug 2024 00:00:00 GMT
DOI: 10.1093/mnras/stae1863
Issue No: Vol. 533, No. 2 (2024)
- Ram-pressure stripped radio tails detected in the dynamically active
environment of the Shapley Supercluster-
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Pages: 1394 - 1411
Abstract: ABSTRACTWe study the radio continuum emission of four galaxies experiencing ram-pressure stripping in four clusters of the Shapley Supercluster at redshift $z\sim 0.05$. Multiband (235–1367 MHz) radio data, complemented by integral-field spectroscopy, allow us to detect and analyse in detail the non-thermal component both in the galaxy discs and the radio continuum tails. Three galaxies present radio continuum tails that are tens of kiloparsecs long. By deriving the radio spectral index in the inner and outer tails and comparing our findings with the distribution of the extraplanar ionized gas and the results of N-body/hydrodynamical simulations, we demonstrate that these tails are caused by the ram pressure, which, together with the ionized gas, sweeps the magnetic field from the galaxy discs. We suggest that the radio continuum emission in these tails can be differently powered by (i) in situ star formation, (ii) relativistic electrons stripped from the disc, and (iii) shock excitation or a combination of them. All the ram-pressure-stripped galaxies are found in environments where cluster–cluster interactions occurred and/or are ongoing, thus strongly supporting the thesis that cluster and group collisions and mergers may locally increase the ram pressure and trigger hydrodynamical interactions between the intracluster medium and the interstellar medium of galaxies.
PubDate: Tue, 06 Aug 2024 00:00:00 GMT
DOI: 10.1093/mnras/stae1867
Issue No: Vol. 533, No. 2 (2024)
- A numerical study of near-Earth asteroid family orbital dispersion
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Pages: 1412 - 1425
Abstract: ABSTRACTWe have studied the evolution of near-Earth asteroid (NEA) families and pairs to inform future searches. To do so, we integrated clusters of simulated NEAs with different initial conditions, namely the orbital inclination, ejection speed, and the effects of mean-motion resonances on the parent body prior to breakup while also varying the orbit, mass, and number of perturbing planetary bodies. We studied the orbital element dispersion rates of NEA family members and found a power-law increase in those families whose orbits brought them close to a planet. This allowed us to conclude that family dispersion is significantly affected by the Kozai–Lidov effect due to oscillations in the eccentricity, and that the rate of dispersion is slowest at high inclination relatively far from the nearest planet. In most cases, the ejection speed of the initial breakup does not affect the dispersion, except within weaker mean-motion resonances where more violent breakups will result in the ejection of a fraction of the asteroids, causing a large increase in dispersion. Within mean-motion resonances, where Kozai–Lidov oscillations are slowed, increases in the dispersion of a family are delayed, leading them to be identifiable for longer.
PubDate: Fri, 02 Aug 2024 00:00:00 GMT
DOI: 10.1093/mnras/stae1874
Issue No: Vol. 533, No. 2 (2024)
- Automation of finding strong gravitational lenses in the Kilo Degree
Survey with U – DenseLens (DenseLens + Segmentation)-
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Pages: 1426 - 1441
Abstract: ABSTRACTIn the context of upcoming large-scale surveys like Euclid, the necessity for the automation of strong lens detection is essential. While existing machine learning pipelines heavily rely on the classification probability (P), this study intends to address the importance of integrating additional metrics, such as Information Content (IC) and the number of pixels above the segmentation threshold ($\rm {\mathit{n}_{s}}$), to alleviate the false positive rate in unbalanced data-sets. In this work, we introduce a segmentation algorithm (U-Net) as a supplementary step in the established strong gravitational lens identification pipeline (Denselens), which primarily utilizes $\rm {\mathit{P}_{mean}}$ and $\rm {IC_{mean}}$ parameters for the detection and ranking. The results demonstrate that the inclusion of segmentation enables significant reduction of false positives by approximately 25 per cent in the final sample extracted from DenseLens, without compromising the identification of strong lenses. The main objective of this study is to automate the strong lens detection process by integrating these three metrics. To achieve this, a decision tree-based selection process is introduced, applied to the Kilo Degree Survey (KiDS) data. This process involves rank-ordering based on classification scores ($\rm {\mathit{P}_{mean}}$), filtering based on Information Content ($\rm {IC_{mean}}$), and segmentation score ($\rm {n_{s}}$). Additionally, the study presents 14 newly discovered strong lensing candidates identified by the U-Denselens network using the KiDS DR4 data.
PubDate: Tue, 06 Aug 2024 00:00:00 GMT
DOI: 10.1093/mnras/stae1882
Issue No: Vol. 533, No. 2 (2024)
- Cometary ion drift energy and temperature at comet
67P/Churyumov–Gerasimeko-
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Pages: 1442 - 1452
Abstract: ABSTRACTThe Ion Composition Analyzer (ICA) on the Rosetta spacecraft observed both the solar wind and the cometary ionosphere around comet 67P/Churyumov–Gerasimenko for nearly two years. However, observations of low energy cometary ions were affected by a highly negative spacecraft potential, and the ICA ion density estimates were often much lower than plasma densities found by other instruments. Since the low energy cometary ions are often the highest density population in the plasma environment, it is nonetheless desirable to understand their properties. To do so, we select ICA data with densities comparable to those of Rosetta’s Langmuir Probe (LAP)/Mutual Impedance Probe (MIP) throughout the mission. We then correct the cometary ion energy distribution of each energy-angle scan for spacecraft potential and fit a drifting Maxwell–Boltzmann distribution, which gives an estimate of the drift energy and temperature for 3521 scans. The resulting drift energy is generally between 11–18 eV and the temperature between 0.5–1 eV. The drift energy shows good agreement with published ion flow speeds from LAP/MIP during the same time period and is much higher than the cometary neutral speed. We see additional higher energy cometary ions in the spectra closest to perihelion that would be well described by a second Maxwellian-like distribution. The energy and temperature are negatively correlated with heliocentric distance, with a stronger dependence on heliocentric distance for temperature. It cannot be quantitatively determined whether this trend is primarily due to heliocentric distance or spacecraft distance to the comet, which increased with decreasing heliocentric distance.
PubDate: Wed, 07 Aug 2024 00:00:00 GMT
DOI: 10.1093/mnras/stae1883
Issue No: Vol. 533, No. 2 (2024)
- Relationship between microwave and metre ranges during an impulsive solar
flare-
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Pages: 1453 - 1462
Abstract: ABSTRACTAn analysis of solar flares with simple temporal structures can help us to understand the features and mechanisms of energy and particle propagation. A weak impulsive solar flare that occurred on 2021 June 3 provided such opportunity. For the purposes of the study, we used microwave observations with spatial resolution from the Siberian Radioheliograph (3–6 GHz) combined with various spectral radio and X-ray data. Flare topology analysis revealed a configuration consisting of a small loop or dome-like structure associated with a compact bright source, and a long high loop system associated with the diffuse source. This indicates a compact and relatively low-lying site of acceleration and initial energy release. The radio metre and the microwave emission demonstrated a peak-to-peak correlation in three of the four bursts. The delays obtained from comparing microwave and metre radio ranges are in good agreement with the delays from the metre dynamic spectrum analysis, but the different radio bursts had different delays. We found that the electron energies derived from metre dynamic spectrum analysis are lower than those shown by hard X-ray emissions. According to the results of theoretical simulations, this can be explained by the expansion of magnetic loops with altitude. The difference in drift velocities for various radio bursts can be the result of the different size of the loop where the electron beams are propagated. This can be a feature related to the configuration type of the studied flare.
PubDate: Fri, 09 Aug 2024 00:00:00 GMT
DOI: 10.1093/mnras/stae1899
Issue No: Vol. 533, No. 2 (2024)
- HELLO project: high-z evolution of large and luminous objects
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Pages: 1463 - 1484
Abstract: ABSTRACTWe present the High-z Evolution of Large and Luminous Objects (HELLO) project, a set of $\sim \!30$ high-resolution cosmological simulations aimed to study Milky Way analogues ($M_\star \sim 10^{10-11}$ ${\mathrm{M}}_{\odot }$) at high redshift ($z\sim [2-4]$). Based on the numerical investigation of a hundred astrophysical objects, HELLO features an updated scheme for chemical enrichment and the addition of local photoionization feedback. Independently of redshift and mass, our galaxies exhibit a smooth progression along the star formation main sequence until $M_\star \sim \!10^{10.5}$, around which our sample at $z \sim 4$ remains mostly unperturbed while the most massive galaxies at $z \sim 2$ reach their peak star formation rate (SFR) and its subsequent decline, due to a mix of gas consumption and stellar feedback. While active galactic nucleus feedback remains subdominant with respect to stellar feedback for energy deposition, its localized nature likely adds to the physical processes leading to declining SFRs. The phase in which a galaxy in our mass range can be found at a given redshift is set by its gas reservoir and assembly history. Finally, our galaxies are in excellent agreement with various scaling relations observed with the Hubble Space Telescope and the JWST, and hence can be used to provide the theoretical framework to interpret current and future observations from these facilities and shed light on the transition from star-forming to quiescent galaxies.
PubDate: Thu, 08 Aug 2024 00:00:00 GMT
DOI: 10.1093/mnras/stae1913
Issue No: Vol. 533, No. 2 (2024)
- The conditional colour–magnitude distribution – II. A comparison of
galaxy colour and luminosity distribution in galaxy groups-
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Pages: 1485 - 1502
Abstract: ABSTRACTThe Conditional Colour-Magnitude Distribution (CCMD) is a comprehensive formalism of the colour–magnitude–halo mass relation of galaxies. With joint modelling of a large sample of SDSS galaxies in fine bins of galaxy colour and luminosity, Xu et al. inferred parameters of a CCMD model that well reproduces colour- and luminosity-dependent abundance and clustering of present-day galaxies. In this work, we provide a test and investigation of the CCMD model by studying the colour and luminosity distribution of galaxies in galaxy groups. An apples-to-apples comparison of group galaxies is achieved by applying the same galaxy group finder to identify groups from the CCMD galaxy mocks and from the SDSS data, avoiding any systematic effect of group finding and mass assignment on the comparison. We find an overall nice agreement in the conditional luminosity function (CLF), the conditional colour function (CCF), and the CCMD of galaxies in galaxy groups inferred from CCMD mock and SDSS data. We also discuss the subtle differences revealed by the comparison. In addition, using two external catalogues constructed to only include central galaxies with halo mass measured through weak lensing, we find that their colour-magnitude distribution shows two distinct and orthogonal components, in line with the prediction of the CCMD model. Our results suggest that the CCMD model provides a good description of halo mass-dependent galaxy colour and luminosity distribution. The halo and CCMD mock catalogues are made publicly available to facilitate other investigations.
PubDate: Wed, 07 Aug 2024 00:00:00 GMT
DOI: 10.1093/mnras/stae1915
Issue No: Vol. 533, No. 2 (2024)
- The dark days are overcast: iron-bearing clouds on HD 209458 b and WASP-43
b can explain low-dayside albedos-
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Pages: 1503 - 1524
Abstract: ABSTRACTWe simulate the geometric albedo spectra of hot Jupiter exoplanets HD 209458 b and WASP-43 b, based on global climate model post-processed with kinetic cloud models. We predict WASP-43 b to be cloudy throughout its dayside, while HD 209458 b has a clear upper atmosphere around the hot subsolar point, largely due to the inclusion of strong optical absorbers TiO and VO in the general circulation model for the latter causes a temperature inversion. In both cases our models find low-geometric albedos – 0.026 for WASP-43 b and 0.028 for HD 209458 b when averaged over the CHaracterizing ExOPlanet Satellite bandpass of $\sim$0.35–1.1 μm – indicating dark daysides, similar to the low albedos measured by observations. We demonstrate the strong impact of clouds that contain Fe-bearing species on the modelled geometric albedos; without Fe-bearing species forming in the clouds, the albedos of both planets would be much higher (0.518 for WASP-43 b, 1.37 for HD 209458 b). We conclude that a cloudy upper or mid-to-lower atmosphere that contains strongly absorbing Fe-bearing aerosol species, is an alternative to a cloud-free atmosphere in explaining the low-dayside albedos of hot Jupiter atmospheres such as HD 209458 b and WASP-43 b.
PubDate: Wed, 07 Aug 2024 00:00:00 GMT
DOI: 10.1093/mnras/stae1916
Issue No: Vol. 533, No. 2 (2024)
- Damping wing absorption associated with a giant Ly α trough at z <
6: direct evidence for late-ending reionization-
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Pages: 1525 - 1540
Abstract: ABSTRACTMultiple observations now suggest that the hydrogen reionization may have ended well below redshift six. While there has previously been no conclusive proof of extended neutral islands in the $z \lt 6$ intergalactic medium, it is possible that such islands give rise to the giant Ly $\alpha$ absorption troughs seen in the spectra of high-redshift quasars. Here, we present evidence that the deepest and longest known Ly $\alpha$ trough at $z \,\lt\, 6$, towards ULAS J0148 + 0600 (J0148), is associated with damping wing absorption. The evidence comes from a window of strong Ly $\alpha$ transmission at the edge of the J0148 proximity zone. We show that the relatively smooth profile of this transmission window is highly unlikely to arise from resonant absorption alone, but is consistent with the presence of a damping wing. We further argue that the damping wing is unlikely to arise from a compact source due to the lack of associated metal lines, and is more likely to arise from an extended neutral island associated with the giant Ly $\alpha$ trough. We investigate the physical conditions that may give rise to the strong transmission window, and speculate that it may signal an usually deep void, nearby ionizing sources, and/or the recent passage of an ionization front.
PubDate: Thu, 15 Aug 2024 00:00:00 GMT
DOI: 10.1093/mnras/stae1918
Issue No: Vol. 533, No. 2 (2024)
- V407 Lup, an intermediate polar nova
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Pages: 1541 - 1549
Abstract: ABSTRACTWe present X-ray and optical observations of nova V407 Lup (Nova Lup 2016), previously well monitored in outburst, as it returned to quiescent accretion. The X-ray light curve in 2020 February revealed a clear flux modulation with a stable period of 564.64 $\pm$ 0.64 s, corresponding to the period measured in outburst and attributed to the spin of a magnetized white dwarf in an intermediate polar (IP) system. This detection in quiescence is consistent with the IP classification proposed after the nova eruption. The XMM–Newton EPIC X-ray flux is ${\simeq} 1.3 \times 10^{-12}$ erg cm$^{-2}$ s$^{-1}$ at a distance, most likely, larger than 5 kpc, emitted in the whole 0.2–12 keV range without a significant cut-off energy. The X-ray spectra are complex; they can be fitted including a power-law component with a relatively flat slope (a power-law index $\simeq$ 1), although, alternatively, a hard thermal component at kT$\ge$ 19 keV also yields a good fit. The SALT optical spectra obtained in 2019 March and 2022 May are quite typical of IPs, with strong emission lines, including some due to a high ionization potential, like He ii at 4685.7 Å. Nebular lines of O [iii] were prominent in 2019 March, but their intensity and equivalent width appeared to be decreasing during that month, and they were no longer detectable in 2022, indicating that the nova ejecta dispersed. Complex profiles of the He ii lines of V407 Lup are also characteristic of IPs, giving further evidence for this classification.
PubDate: Fri, 09 Aug 2024 00:00:00 GMT
DOI: 10.1093/mnras/stae1922
Issue No: Vol. 533, No. 2 (2024)
- An improved Tully–Fisher estimate of H0
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Pages: 1550 - 1559
Abstract: ABSTRACTWe propose an improved comprehensive method for determining the Hubble constant ($H_0$) using the Tully–Fisher relation. By fitting a peculiar velocity model in conjunction with the Tully–Fisher relation, all available data can be used to derive self-consistent Tully–Fisher parameters. In comparison to previous approaches, our method offers several improvements: it can be readily generalized to different forms of the Tully–Fisher relation and its intrinsic scatter; it uses a peculiar velocity model to predict distances more accurately; it can account for all selection effects; it uses the entire data set to fit the Tully–Fisher relation; and it is fully self-consistent. The Tully–Fisher relation zero-point is calibrated using the subset of galaxies with distances from absolute distance indicators. We demonstrate this method on the Cosmicflows-4 catalogue i-band and $W1$-band Tully–Fisher samples and show that the uncertainties from fitting the Tully–Fisher relation amount to only 0.2 km s$^{-1}$ Mpc$^{-1}$. Using all available absolute distance calibrators, we obtain $H_0=73.3$ $\pm$ 2.1 (stat) $\pm$ 3.5 (sys) km s$^{-1}$ Mpc$^{-1}$, where the statistical uncertainty is dominated by the small number of galaxies with absolute distance estimates. The substantial systematic uncertainty reflects inconsistencies between various zero-point calibrations of the Cepheid period–luminosity relation, the tip of the red giant branch standard candle, and the Type Ia supernova standard candle. However, given a reliable set of absolute distance calibrators, our method promises enhanced precision in $H_0$ measurements from large new Tully–Fisher samples such as the WALLABY survey.
PubDate: Thu, 08 Aug 2024 00:00:00 GMT
DOI: 10.1093/mnras/stae1925
Issue No: Vol. 533, No. 2 (2024)
- Probing solar wind velocity from simultaneous superior solar conjunction
radio science experiments of BepiColombo and Akatsuki missions-
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Pages: 1560 - 1567
Abstract: ABSTRACTA radio link directly probing the inner solar corona offers the possibility to characterize solar wind properties, including velocity, density, turbulence, and even the axial ratio. In this study, we leveraged radiometric data obtained during a joint superior solar conjunction of the ESA/JAXA BepiColombo mission and the JAXA Akatsuki mission. Our objective is to ascertain the solar wind velocity by analysing Doppler-shift timeseries of radio signals exchanged between the two spacecraft and two distinct ground stations. We conducted a cross-correlation analysis to determine the travel time of large-scale plasma density fluctuations as they intersect with the downlink signals of both spacecraft. This method is applied to the data collected on 2021 March 13 and 2021 March 14. The analysis of the March 13 data has shown that the two Doppler residuals timeseries present a clear correlation at a time-lag of 2910 s. Using the knowledge of the relative distance between the two probe-ground station lines of sight at the closest approach to the Sun, we estimated the solar wind velocity to be $421\pm 21$ km s−1. Following the same procedure for the second experiment, we estimated the solar wind speed velocity to be $336\pm 7$ km s−1. These results are compatible with the sampling of the slow solar wind at heliographic latitudes of $-22^\circ$ and $-26^\circ$, respectively.
PubDate: Fri, 09 Aug 2024 00:00:00 GMT
DOI: 10.1093/mnras/stae1929
Issue No: Vol. 533, No. 2 (2024)
- Imprints of supermassive black hole evolution on the spectral and spatial
anisotropy of nano-hertz stochastic gravitational-wave background-
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Pages: 1568 - 1582
Abstract: ABSTRACTThe formation and evolution of supermassive black holes (SMBHs) remains an open question in the field of modern cosmology. The detection of nanohertz (n-Hz) gravitational waves via pulsar timing arrays (PTAs) in the form of individual events and the stochastic gravitational wave background (SGWB) offers a promising avenue for studying SMBH evolution across cosmic time, with SGWB signal being the immediately detectable signal with the currently accessible telescope sensitivities. By connecting the galaxy properties in the large scale (Gpc scale) cosmological simulation such as MICECAT with the small scale ($\sim$Mpc scale) galaxy simulations from ROMULUS, we show that different scenarios of galaxy–SMBH evolution with redshift leads to a frequency-dependent spatial anisotropy in the SGWB signal. The presence of slow evolution of the SMBHs in the Universe leads to a pronounced blue anisotropic spectrum of the SGWB. In contrast, if SMBHs grow faster in the Universe in lighter galaxies, the frequency-dependent spatial anisotropy exhibits a more flattened anisotropic spectrum. This additional aspect of the SGWB signal on top of the monopole SGWB signal, can give insight on how the SMBHs form in the high-redshift Universe and its interplay with the galaxy formation from future measurements.
PubDate: Sat, 10 Aug 2024 00:00:00 GMT
DOI: 10.1093/mnras/stae1930
Issue No: Vol. 533, No. 2 (2024)
- Correlations of methyl formate (CH3OCHO), dimethyl ether (CH3OCH3), and
ketene (H2CCO) in high-mass star-forming regions-
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Pages: 1583 - 1617
Abstract: ABSTRACTWe present high-spatial resolution (0.7–1.0 arcsec) submillimeter observations of continuum and molecular lines of CH$_{3}$OCHO, CH$_{3}$OCH$_{3}$, and H$_{2}$CCO toward 11 high-mass star-forming regions using the Atacama large millimetre/submillimetre array (ALMA). A total of 19 separate cores from nine high-mass star-forming regions are found to be line-rich, including high-, intermediate-, and low-mass line-rich cores. The three molecules are detected in these line-rich cores. We map the emission of CH$_{3}$OCHO, CH$_{3}$OCH$_{3}$, and H$_{2}$CCO in nine high-mass star-forming regions. The spatial distribution of the three molecules is very similar and concentrated in the areas of intense continuum emission. We also calculate the rotation temperatures, column densities, and abundances of CH$_{3}$OCHO, CH$_{3}$OCH$_{3}$, and H$_{2}$CCO under the local thermodynamic equilibrium assumption. The abundances relative to H$_{2}$ and CH$_{3}$OH, and line widths of the three molecules are significantly correlated. The abundances relative to H$_{2}$, temperatures, and line widths of the three molecules tend to be higher in cores with higher mass and outflows detected. The possible chemical links of the three molecules are discussed.
PubDate: Tue, 13 Aug 2024 00:00:00 GMT
DOI: 10.1093/mnras/stae1934
Issue No: Vol. 533, No. 2 (2024)
- Frequency shift in binary microlensing
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Pages: 1618 - 1628
Abstract: ABSTRACTGravitational microlensing with binary lensing is one of the channels for detecting exoplanets. Due to the degeneracy of the lens parameters for the binary microlensing, additional features such as parallax and finite-size effects need to identify the lens parameters. The frequency-shift effect as the relativistic analogy of the gravity assist for the photons, is an extra observation that provides additional constraint between the lens parameters. In this work, we extend the application of the frequency-shift effect to binary microlensing and derive the frequency shift during the lensing and caustic crossing. The frequency shift for the binary lens is of the order of ${\Delta \nu }/{\nu }\sim 10^{-12}$. We also investigate the feasibility of detecting this effect by employing cross-correlation methods.
PubDate: Mon, 12 Aug 2024 00:00:00 GMT
DOI: 10.1093/mnras/stae1938
Issue No: Vol. 533, No. 2 (2024)
- X-ray afterglow limits on the viewing angles of short gamma-ray bursts
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Pages: 1629 - 1648
Abstract: ABSTRACTThe behaviour of a short gamma-ray burst (sGRB) afterglow light curve can reveal the angular structure of the relativistic jet and constrain the observer’s viewing angle $\theta _\textrm {obs}$. The observed deceleration time of the jet, and, therefore, the time of the afterglow peak, depends on the observer’s viewing angle. A larger viewing angle leads to a later peak of the afterglow and a lower flux at peak. We utilize the earliest afterglow detections of 58 sGRBs detected with the Neil Gehrels Swift Observatory X-ray Telescope to constrain the ratio of the viewing angle $\theta _\textrm {obs}$ to the jet’s core $\theta _\textrm {c}$. We adopt a power-law angular jet structure in both energy $E(\theta)\propto \theta ^{-a}$ and Lorentz factor $\Gamma (\theta)\propto \theta ^{-b}$ beyond the core. We find that either sGRBs are viewed within $\theta _\textrm {obs}/\theta _\textrm {c}\lt 1$ or the initial Lorentz factor of material in their jet’s core is extremely high ($\Gamma _0\gt 500$). If we consider tophat jets, we constrain 90 per cent of our sample to be viewed within $\theta _\textrm {obs}/\theta _\textrm {c}\lt 1.06$ and 1.15 for our canonical and conservative afterglow scenarios. For a subset of events with measurements of the jet break, we can constrain $\Gamma _0\theta _\textrm {c}\gtrsim 30$. This confirmation that cosmological sGRBs are viewed either on-axis or very close to their jet’s core has significant implications for the nature of the prompt gamma-ray production mechanism and for the rate of future sGRB detections coincident with gravitational waves, implying that they are extremely rare.
PubDate: Mon, 12 Aug 2024 00:00:00 GMT
DOI: 10.1093/mnras/stae1941
Issue No: Vol. 533, No. 2 (2024)
- Formation of the AlCl molecule through radiative association of Al with Cl
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Pages: 1649 - 1653
Abstract: ABSTRACTDetection of the AlCl molecule in IRC+10216 has been reported in the literature. We here report calculations of reaction rate constants for formation of AlCl through radiative association of Al and Cl for a temperature interval of 1000 to 14000 K. Potential energy and permanent/transition dipole moment curves were taken from the literature. Quantum mechanical and semiclassical/classical methods were used to obtain the reaction cross-sections and thermal rate constants, accounting for shape resonances with Breit–Wigner theory. Both the A$^1 \Pi \rightarrow$ X$^1 \Sigma ^+$ transition and the X$^1 \Sigma ^+\rightarrow$ X$^1 \Sigma ^+$ transition have been treated, with results showing that the former dominates for the temperatures considered in this study. Our rate constants are a factor of two to three larger than previously calculated values, where the latter were obtained without considering resonances or the X$^1 \Sigma ^+\rightarrow$ X$^1 \Sigma ^+$ transition. Our new values do however not change the previous conclusion that radiative association can only contribute modestly to the formation of AlCl under the given conditions.
PubDate: Mon, 12 Aug 2024 00:00:00 GMT
DOI: 10.1093/mnras/stae1942
Issue No: Vol. 533, No. 2 (2024)
- Primeval very low-mass stars and brown dwarfs – VIII. The first age
benchmark L subdwarf, a wide companion to a halo white dwarf-
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Pages: 1654 - 1669
Abstract: ABSTRACTWe report the discovery of five white dwarf + ultracool dwarf systems identified as common proper motion wide binaries in the Gaia Catalogue of Nearby Stars. The discoveries include a white dwarf + L subdwarf binary, VVV 1256−62AB, a gravitationally bound system located 75.6$^{+1.9}_{-1.8}$ pc away with a projected separation of 1375$^{+35}_{-33}$ au. The primary is a cool DC white dwarf with a hydrogen dominated atmosphere, and has a total age of $10.5^{+3.3}_{-2.1}$ Gyr, based on white dwarf model fitting. The secondary is an L subdwarf with a metallicity of [M/H] = $-0.72^{+0.08}_{-0.10}$ (i.e. [Fe/H] = $-0.81\pm 0.10$) and $T_{\rm eff}$ = 2298$^{+45}_{-43}$ K based on atmospheric model fitting of its optical to near infrared spectrum, and likely has a mass just above the stellar/substellar boundary. The subsolar metallicity of the L subdwarf and the system’s total space velocity of 406 km s−1 indicates membership in the Galactic halo, and it has a flat eccentric Galactic orbit passing within 1 kpc of the centre of the Milky Way every $\sim$0.4 Gyr and extending to 15–31 kpc at apogal. VVV 1256−62B is the first L subdwarf to have a well-constrained age, making it an ideal benchmark of metal-poor ultracool dwarf atmospheres and evolution.
PubDate: Mon, 05 Aug 2024 00:00:00 GMT
DOI: 10.1093/mnras/stae1851
Issue No: Vol. 533, No. 2 (2024)
- A fourth-order accurate finite volume scheme for resistive relativistic
MHD-
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Pages: 1670 - 1686
Abstract: ABSTRACTWe present a finite-volume, genuinely fourth-order accurate numerical method for solving the equations of resistive relativistic magnetohydrodynamics in Cartesian coordinates. In our formulation, the magnetic field is evolved in time in terms of face-average values via the constrained-transport method, while the remaining variables (density, momentum, energy, and electric fields) are advanced as cell volume averages. Spatial accuracy employs fifth-order accurate WENO-Z reconstruction from point values (as described in a companion paper) to obtain left and right states at zone interfaces. Explicit flux evaluation is carried out by solving a Riemann problem at cell interfaces, using the Maxwell–Harten–Lax–van Leer with contact wave resolution. Time-stepping is based on the implicit–explicit Runge–Kutta (RK) methods, of which we consider both the third-order strong stability preserving SSP3(4,3,3) and a recent fourth-order additive RK scheme, to cope with the stiffness introduced by the source term in Ampere’s law. Numerical benchmarks are presented in order to assess the accuracy and robustness of our implementation.
PubDate: Thu, 18 Jul 2024 00:00:00 GMT
DOI: 10.1093/mnras/stae1729
Issue No: Vol. 533, No. 2 (2024)
- Turbocharging constraints on dark matter substructure through a synthesis
of strong lensing flux ratios and extended lensed arcs-
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Pages: 1687 - 1713
Abstract: ABSTRACTStrong gravitational lensing provides a purely gravitational means to infer properties of dark matter haloes and thereby constrain the particle nature of dark matter. Strong lenses sometimes appear as four lensed images of a background quasar accompanied by spatially resolved emission from the quasar host galaxy encircling the main deflector (lensed arcs). We present methodology to simultaneously reconstruct lensed arcs and relative image magnifications (flux ratios) in the presence of full populations of subhaloes and line-of-sight haloes. To this end, we develop a new approach for multiplane ray tracing that accelerates lens mass and source light reconstruction by factors of $\sim\!\! 100\!\!-\!\!1000$. Using simulated data, we show that simultaneous reconstruction of lensed arcs and flux ratios isolates small-scale perturbations to flux ratios by dark matter substructure from uncertainties associated with the main deflector mass profile on larger angular scales. Relative to analyses that use only image positions and flux ratios to constrain the lens model, incorporating arcs strengthens likelihood ratios penalizing warm dark matter with a suppression scale $m_{\rm {hm}} / {\rm M}_{\odot }$ in the ranges of $\left[10^7 \!\!-\!\! 10^{7.5}\right]$, $\left[10^{7.5} \!\!-\!\! 10^{8}\right]$, $\left[10^8 \!\!-\!\! 10^{8.5}\right]$, and $\left[10^{8.5} \!\!-\!\! 10^{9}\right]$ by factors of 1.3, 2.5, 5.6, and 13.1, respectively, for a cold dark matter ground truth. The 95 per cent exclusion limit improves by 0.5 dex in $\log _{10} m_{\rm {hm}}$. The enhanced sensitivity to low-mass haloes enabled by these methods pushes the observational frontier of substructure lensing to the threshold of galaxy formation, enabling stringent tests of any theory that alters the properties of dark matter haloes.
PubDate: Fri, 26 Jul 2024 00:00:00 GMT
DOI: 10.1093/mnras/stae1810
Issue No: Vol. 533, No. 2 (2024)
- Hyperfine structure of the methanol molecule as traced by Class I
methanol masers-
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Pages: 1714 - 1732
Abstract: ABSTRACTWe present results on simultaneous observations of Class I methanol masers at 25, 36, and 44 GHz towards 22 Galactic targets carried out with the Effelsberg 100-m telescope. The study investigates relations between the hyperfine (HF) structure of the torsion–rotation transitions in CH$_3$OH and maser activity. By analysing the radial velocity shifts between different maser lines together with the patterns of the HF structure based on laboratory measurements and quantum-chemical calculations, we find that in any source only one specific HF transition forms the maser emission and that this transition changes from source to source. The physical conditions leading to this selective behaviour are still unclear. Using accurate laboratory rest frequencies for the 25 GHz transitions, we have refined the centre frequencies for the HF multiplets at 36, 44, and 95 GHz: $f_{\scriptscriptstyle 36} = (36169.2488\pm 0.0002_{\scriptscriptstyle \rm stat} \pm 0.0004_{\scriptscriptstyle \rm sys})$ MHz. $f_{\scriptscriptstyle 44} = (44069.4176\pm 0.0002_{\scriptscriptstyle \rm stat} \pm 0.0004_{\scriptscriptstyle \rm sys})$ MHz, and $f_{\scriptscriptstyle 95} = (95169.4414\pm 0.0003_{\scriptscriptstyle \rm stat} \pm 0.0004_{\scriptscriptstyle \rm sys})$ MHz. Comparison with previous observations of 44 GHz masers performed 6–10 yr ago with a Korean 21-m Korean Very Long Baseline Interferometry Network telescope towards the same targets confirms the kinematic stability of Class I maser line profiles during this time interval and reveals a systematic radial velocity shift of $0.013\pm 0.005$ km s$^{-1}$ between the two telescopes.
PubDate: Sat, 27 Jul 2024 00:00:00 GMT
DOI: 10.1093/mnras/stae1815
Issue No: Vol. 533, No. 2 (2024)
- AGN-driven outflows in clumpy media: multiphase structure and scaling
relations-
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Pages: 1733 - 1755
Abstract: ABSTRACTSmall-scale winds driven from accretion discs surrounding active galactic nuclei (AGN) are expected to launch kpc-scale outflows into their host galaxies. However, the ways in which the structure of the interstellar medium (ISM) affects the multiphase content and impact of the outflow remain uncertain. We present a series of numerical experiments featuring a realistic small-scale AGN wind with velocity $5\times 10^3 \!-\! 10^4\rm {\ km\ s^{-1}}$ interacting with an isolated galaxy disc with a manually controlled clumpy ISM, followed at sub-pc resolution. Our simulations are performed with arepo and probe a wide range of AGN luminosities ($L_{\rm {AGN}}{=} 10^{43-47}\rm {\ erg\ s^{-1}}$) and ISM substructures. In homogeneous discs, the AGN wind sweeps up an outflowing, cooling shell, where the emerging cold phase dominates the mass and kinetic energy budgets, reaching a momentum flux $\dot{p} \approx 7\ L/c$. However, when the ISM is clumpy, outflow properties are profoundly different. They contain small, long-lived ($\gtrsim 5\ \rm {Myr}$), cold ($T{\lesssim }10^{4.5}{\rm {\ K}}$) cloudlets entrained in the faster, hot outflow phase, which are only present in the outflow if radiative cooling is included in the simulation. While the cold phase dominates the mass of the outflow, most of the kinetic luminosity is now carried by a tenuous, hot phase with $T \gtrsim 10^7 \, \rm K$. While the hot phases reach momentum fluxes $\dot{p} \approx (1 - 5)\ L/c$, energy-driven bubbles couple to the cold phase inefficiently, producing modest momentum fluxes $\dot{p} \lesssim L/c$ in the fast-outflowing cold gas. These low momentum fluxes could lead to the outflows being misclassified as momentum-driven using common observational diagnostics. We also show predictions for scaling relations between outflow properties and AGN luminosity and discuss the challenges in constraining outflow driving mechanisms and kinetic coupling efficiencies using observed quantities.
PubDate: Fri, 26 Jul 2024 00:00:00 GMT
DOI: 10.1093/mnras/stae1816
Issue No: Vol. 533, No. 2 (2024)
- The frequency of transiting planetary systems around polluted white dwarfs
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Pages: 1756 - 1765
Abstract: ABSTRACTThis paper investigates the frequency of transiting planetary systems around metal-polluted white dwarfs using high-cadence photometry from ULTRACAM and ULTRASPEC on the ground and space-based observations with TESS. Within a sample of 313 metal-polluted white dwarfs with available TESS light curves, two systems known to have irregular transits are blindly recovered by box-least-squares and Lomb–Scargle analyses, with no new detections, yielding a transit fraction of $0.8_{-0.4}^{+0.6}$ per cent. Planet detection sensitivities are determined using simulated transit injection and recovery for all light curves, producing upper limit occurrences over radii from dwarf to Kronian planets, with periods from 1 h to 27 d. The dearth of short-period, transiting planets orbiting polluted white dwarfs is consistent with engulfment during the giant phases of stellar evolution, and modestly constrains dynamical re-injection of planets to the shortest orbital periods. Based on simple predictions of transit probability, where $(R_* + R_{\rm p})/a\simeq 0.01$, the findings here are nominally consistent with a model where 100 per cent of polluted white dwarfs have circumstellar debris near the Roche limit; however, the small sample size precludes statistical confidence in this result. Single transits are also ruled out in all light curves using a search for correlated outliers, providing weak constraints on the role of Oort-like comet clouds in white dwarf pollution.
PubDate: Thu, 01 Aug 2024 00:00:00 GMT
DOI: 10.1093/mnras/stae1859
Issue No: Vol. 533, No. 2 (2024)
- Disc novae: thermodynamics of gas-assisted binary black hole formation in
AGN discs-
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Pages: 1766 - 1781
Abstract: ABSTRACTWe investigate the thermodynamics of close encounters between stellar mass black holes (BHs) in the gaseous discs of active galactic nuclei (AGNs), during which binary black holes (BBHs) may form. We consider a suite of 2D viscous hydrodynamical simulations within a shearing box prescription using the Eulerian grid code athena++. We study formation scenarios where the fluid is either an isothermal gas or an adiabatic mixture of gas and radiation in local thermal equilibrium. We include the effects of viscous and shock heating, as well as optically thick cooling. We co-evolve the embedded BHs with the gas, keeping track of the energetic dissipation and torquing of the BBH by gas and inertial forces. We find that compared to the isothermal case, the minidiscs formed around each BH are significantly hotter and more diffuse, though BBH formation is still efficient. We observe massive blast waves arising from collisions between the radiative minidiscs during both the initial close encounter and subsequent periapsis periods for successfully bound BBHs. These ‘disc novae’ have a profound effect, depleting the BBH Hill sphere of gas and injecting energy into the surrounding medium. In analysing the thermal emission from these events, we observe periodic peaks in local luminosity associated with close encounters/periapses, with emission peaking in the optical/near-infrared (IR). In the AGN outskirts, these outbursts can reach 4 per cent of the AGN luminosity in the IR band, with flares rising over 0.5–1 yr. Collisions in different disc regions, or when treated in 3D with magnetism, may produce more prominent flares.
PubDate: Mon, 05 Aug 2024 00:00:00 GMT
DOI: 10.1093/mnras/stae1866
Issue No: Vol. 533, No. 2 (2024)
- Structural properties of subgroups of stars associated with open clusters
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Pages: 1782 - 1799
Abstract: ABSTRACTRecent studies have identified star clusters with multiple components based on accurate spatial distributions and/or proper motions from Gaia Data Release 3 (DR3), utilizing diverse diagnostics to gain an understanding of subgroup evolution. These findings motivated us to search for subgroups among the objects examined in our previous work, which employed fractal statistics. The present study considers seven open clusters that exhibit significant dispersion in age and/or proper motion distributions, suggesting that they are not single clusters. In order to characterize the stellar groups, we calculate the membership probability using Bayesian multidimensional analysis by fitting the observed proper motion distribution of the candidates. A probability distribution is also used to determine the distance of the cluster, which is obtained from the mean value of the distance modes. The photometry from Gaia DR3 is compared with evolutionary models to estimate the cluster age and total mass. In our sample, double components are found only for Markarian 38 and NGC 2659. The other five clusters are confirmed as being single. The structural parameters, such as $\mathcal {Q}$, $\Lambda _{\rm MSR}$, and $\Sigma _{\rm LDR}$, are compared with results from N-body simulations to investigate how the morphology of the stellar clustering evolves. The new results, for a more complete sample of cluster members, provide a better definition of the distribution type (central concentration or substructured region) inferred from the $\overline{m} - \overline{s}$ plot.
PubDate: Fri, 23 Aug 2024 00:00:00 GMT
DOI: 10.1093/mnras/stae1869
Issue No: Vol. 533, No. 2 (2024)
- Radio observations of the 2022 outburst of the transitional Z-Atoll source
XTE J1701−462-
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Pages: 1800 - 1807
Abstract: ABSTRACTXTE J1701−462 is a neutron star low-mass X-ray binary (NS LMXB) discovered in 2006 as the first system to demonstrate unambiguously that the ‘Atoll’ and ‘Z’ classes of accreting neutron stars are separated by accretion rate. Radio observations during the 2006/7 outburst provided evidence for the formation of a relativistic jet, as now expected for all accreting neutron star and black hole X-ray binaries at high-accretion rates. The source entered a new outburst in 2022, and we report 29 observations made with the MeerKAT radio telescope. The first radio detection was on the 16th September 2022, we continued detecting the source until mid-December 2022. Thereafter, establishing radio upper limits till 25 March 2023. We present the radio analysis alongside analysis of contemporaneous X-ray observations from MAXI. The radio light curve shows evidence for at least three flare-like events over the first hundred days, the most luminous of which has an associated minimum energy of $1\times 10^{38}$ erg. We provide a detailed comparison with the 2006/7 outburst, and demonstrate that we detected radio emission from the source for considerably longer in the more recent outburst, although this is probably a function of sampling. We further constrain the radio emission from the source to have a polarization of less than 9 per cent at the time of 2022 IXPE detection of X-ray polarization. Finally, we place the source in the radio–X-ray plane, demonstrating that when detected in radio it sits in a comparable region of parameter space to the other Z-sources.
PubDate: Fri, 02 Aug 2024 00:00:00 GMT
DOI: 10.1093/mnras/stae1875
Issue No: Vol. 533, No. 2 (2024)
- Galaxy build-up in the first 1.5 Gyr of cosmic history: insights from the
stellar mass function at z ~ 4–9 from JWST NIRCam observations-
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Pages: 1808 - 1838
Abstract: ABSTRACTCombining the public JWST/NIRCam imaging programs CEERS, PRIMER, and JADES, spanning a total area of $\sim 500\, {\rm arcmin}^2$, we obtain a sample of $\gt $30 000 galaxies at $z_{\rm phot}\sim 4\!-\!9$ that allows us to perform a complete, rest-optical-selected census of the galaxy population at $z\gt 3$. Comparing the stellar mass $M_*$ and the UV-slope $\beta$ distributions between JWST- and HST-selected samples, we generally find very good agreement and no significant biases. Nevertheless, JWST enables us to probe a new population of UV-red galaxies that was missing from previous HST-based Lyman-break galaxy (LBG) samples. We measure galaxy stellar mass functions (SMFs) at $z\sim 4\!-\!9$ down to limiting masses of $10^{7.5}\!-\!10^{8.5}\, {\rm M_\odot }$, finding steep low-mass slopes over the entire redshift range, reaching values of $\alpha \approx -2$ at $z\gtrsim 6$. At the high-mass end, UV-red galaxies dominate at least out to $z\sim 6$. The implied redshift evolution of the SMF suggests a rapid build-up of massive dust-obscured or quiescent galaxies from $z\sim 6$ to $z\sim 4$ as well as an enhanced efficiency of star formation towards earlier times ($z\gtrsim 6$). Finally, we show that the galaxy mass density grows by a factor $\sim 20\times$ from $z\sim 9$ to $z\sim 4$. Our results emphasize the importance of rest-frame optically selected samples in inferring accurate distributions of physical properties and studying the mass build-up of galaxies in the first 1.5 Gyr of cosmic history.
PubDate: Thu, 08 Aug 2024 00:00:00 GMT
DOI: 10.1093/mnras/stae1891
Issue No: Vol. 533, No. 2 (2024)
- Costless correction of chain based nested sampling parameter estimation in
gravitational wave data and beyond-
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Pages: 1839 - 1851
Abstract: ABSTRACTNested sampling parameter estimation differs from evidence estimation, in that it incurs an additional source of uncertainty. This uncertainty affects estimates of parameter means and credible intervals in gravitational wave analyses and beyond, and yet, it is typically not accounted for in standard uncertainty estimation methods. In this paper, we present two novel methods to quantify this uncertainty more accurately for any chain based nested sampler, using the additional likelihood calls made at run time in producing independent samples. Using injected signals of black hole binary coalescences as an example, we first show concretely that the usual uncertainty estimation method is insufficient to capture the true error bar on parameter estimates. We then demonstrate how the extra points in the chains of chain based samplers may be carefully utilized to estimate this uncertainty correctly, and provide a way to check the accuracy of the resulting error bars. Finally, we discuss how this uncertainty affects p–p plots and coverage assessments.
PubDate: Wed, 07 Aug 2024 00:00:00 GMT
DOI: 10.1093/mnras/stae1908
Issue No: Vol. 533, No. 2 (2024)
- Forecasting galaxy cluster H i mass recovery with CHIME at redshifts
z = 1 and 2 via the IllustrisTNG simulations-
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Pages: 1852 - 1864
Abstract: ABSTRACTThe Canadian Hydrogen Intensity Mapping Experiment (CHIME) is a drift-scan interferometer designed to map the entire northern sky every 24 h. The all-sky coverage and sensitivity to neutral hydrogen flux at intermediate redshifts makes the instrument a resource for other exciting science in addition to cosmology for which it was originally designed. Here, we demonstrate its utility for the study of the H i content of galaxy populations across environments and redshifts. We use simulated data from the IllustrisTNG project to generate mock CHIME-like intensity maps, which we cross-correlate with various tracers – including galaxies and galaxy clusters – to recover aggregate H i signals from stacking analyses. We find that there is more flux in stacks on galaxy clusters or cluster member galaxies compared to those on a general galaxy catalogue due to the enhanced number of H i-rich sources included in the CHIME primary beam. We report that it is possible to infer an average $M_\mathrm{HI}$ for clusters as a function of redshift and selection criteria from the signal in their averaged stacks despite the instrument’s low spatial resolution. This proof-of-concept result opens up a promising, and timely, new avenue to measure the evolution of the neutral hydrogen content in intermediate-to-high redshift galaxy clusters via cross-correlation of galaxy cluster catalogues with 21-cm intensity maps.
PubDate: Thu, 08 Aug 2024 00:00:00 GMT
DOI: 10.1093/mnras/stae1919
Issue No: Vol. 533, No. 2 (2024)
- Generalized emergent dark energy in the late-time Universe
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Pages: 1865 - 1873
Abstract: ABSTRACTWe investigate a new type of dark energy model called the generalized emergent dark energy (GEDE) model which encodes either phenomenologically emergent dark energy that has no effective presence in the early times and emerges strongly in late times or the standard model of cosmology Lambda cold dark matter ($\Lambda$CDM). We test this new brand dark energy model and compare it with the standard model of cosmology $\Lambda$CDM using the final baryon acoustic oscillation (BAO) uncorrelated measurements in the effective redshift range $0.106 \le z \le 2.33$ of different surveys after two decades of dedicated spectroscopic observation combined with the compressed form of the Pantheon sample of Type Ia supernovae, the observational $H(z)$ measurements based on differential age method, and the recent Hubble constant value measurement from the Hubble Space Telescope and the SH0ES Team in 2022 as an additional Gaussian prior. In the GEDE model fit yields the cosmological parameters $\Omega _{m}=0.2713 \pm 0.0142$ and $\Omega _{\Lambda }=0.7245 \pm 0.0126$ for BAO + R22. Combining BAO with the observational $H(z)$ measurements based on the differential age method, and the Pantheon Type Ia supernova, the Hubble constant yields 69.92 $\pm$ 1.17 km s$^{-1}$ Mpc$^{-1}$ and the sound horizon gives 145.97 $\pm$ 2.44 Mpc. We perform the Akaike information criteria, Bayesian information criterion, and Bayesian evidence to compare the GEDE and $\Lambda$CDM models and see that $\Lambda$CDM has a better performance without the inclusion of early-time observations as the cosmic microwave background.
PubDate: Thu, 08 Aug 2024 00:00:00 GMT
DOI: 10.1093/mnras/stae1920
Issue No: Vol. 533, No. 2 (2024)
- Correction to: The XXL Survey. XLVII. The L X − σv relation of galaxy
groups and clusters detected in the XXL and GAMA surveys-
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Pages: 1874 - 1874
Abstract: This is a correction to: P. A. Giles, A. Robotham, M. E. Ramos-Ceja, B. J. Maughan, M. Sereno, S. McGee, S. Phillipps, A. Iovino, D. J. Turner, C. Adami, S. Brough, L. Chiappetti, S. P. Driver, A. E. Evrard, A. Farahi, F. Gastaldello, B. W. Holwerda, A. M. Hopkins, E. Koulouridis, F. Pacaud, M. Pierre, K. A. Pimbblet, The XXL Survey. XLVII. The L X − $\sigma\,_{v}$ relation of galaxy groups and clusters detected in the XXL and GAMA surveys, Monthly Notices of the Royal Astronomical Society, Volume 511, Issue 1, March 2022, Pages 1227–1246, https://doi.org/10.1093/mnras/stab3626.
PubDate: Fri, 23 Aug 2024 00:00:00 GMT
DOI: 10.1093/mnras/stae1933
Issue No: Vol. 533, No. 2 (2024)
- Structure functions with higher-order stencils as a probe to separate
small- and large-scale magnetic fields-
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Pages: 1875 - 1886
Abstract: ABSTRACTMagnetic fields are an energetically important component of star formation galaxies, but it is often difficult to measure their properties from observations. One of the complexities stems from the fact that the magnetic fields, especially in spiral galaxies, have a two-scale nature: a large-scale field, coherent over kpc scales, and a small-scale random field, with a scale of ${\lesssim} 100 \, {\rm pc}$. Moreover, it is known that the strength of small- and large-scale fields is comparable and this makes it even harder to find their imprints in radio polarization observations such as the Faraday rotation measure (RM), which is the integral over the path-length of the product of the thermal electron density and the parallel component of the magnetic field to the line of sight. Here, we propose and demonstrate the use of second-order structure functions of RM computed with multiple higher-order stencils as a powerful analysis to separate the small- and large-scale magnetic field components. In particular, we provide new methods and calibrations to compute the scale and the strength of the large-scale magnetic field in the presence of small-scale magnetic fluctuations. We then apply the method to find the scale of large-scale magnetic fields in the nearby galaxies M51 and NGC 6946, using archival data, and further discuss the need for computing the RM structure functions with higher-order stencils. With multiple modern radio polarization observatories and eventually the Square Kilometre Array, RM observations will significantly improve in quantity and quality, and the higher-order stencil structure function techniques developed here can be used to extract information about multiscale magnetic fields in galaxies.
PubDate: Sat, 10 Aug 2024 00:00:00 GMT
DOI: 10.1093/mnras/stae1935
Issue No: Vol. 533, No. 2 (2024)
- Gravitational interactions of binary systems in the massive planetesimal
disc-
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Pages: 1887 - 1893
Abstract: ABSTRACTThe prevalence of binary systems within our Solar system has become a common phenomenon, with over 500 systems identified. However, the connection that exists between the different dynamic mechanisms that give rise to their intricate orbital structure and the durability of these systems over time continues to be the subject of intense research. Encouraged by several works indicating that the number of binaries would have been much greater at the beginning of the outer Solar system, in our study we delve into the dynamical evolution of binary objects within the primordial populations of the massive disc of planetesimals between 15 and 30 au. By concentrating specifically on gravitational disturbances caused by neighbouring bodies, the research aims to investigate the effects on orbital dynamics resulting from the presence of binary objects to different extents within the studied populations. The results of our experiments indicate that populations with different binary fractions would not engender significantly divergent changes in the orbits of the study objects after 100 Myr of evolution. The survival of these systems, only considering a scenario of encounters and collisions between neighbours, would not have occurred in large quantities, being even lower in the outermost regions of the disc (25–30 au).
PubDate: Tue, 20 Aug 2024 00:00:00 GMT
DOI: 10.1093/mnras/stae1937
Issue No: Vol. 533, No. 2 (2024)
- Optically quiet, but FUV loud: results from comparing the far-ultraviolet
predictions of flare models with TESS and HST-
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Pages: 1894 - 1906
Abstract: ABSTRACTThe far-ultraviolet (FUV) flare activity of low-mass stars has become a focus in our understanding of the exoplanet atmospheres and how they evolve. However, direct detection of FUV flares and measurements of their energies and rates are limited by the need for space-based observations. The difficulty of obtaining such observations may push some works to use widely available optical data to calibrate multiwavelength spectral models that describe UV and optical flare emission. These models either use single temperature blackbody curves to describe this emission, or combine a blackbody curve with archival spectra. These calibrated models would then be used to predict the FUV flare rates of low-mass stars of interest. To aid these works, we used TESS optical photometry and archival HST FUV spectroscopy to test the FUV predictions of literature flare models. We tested models for partially (M0–M2) and fully convective (M4–M5) stars, 40 Myr and field age stars, and optically quiet stars. We calculated FUV energy correction factors that can be used to bring the FUV predictions of tested models in line with observations. A flare model combining optical and NUV blackbody emission with FUV emission based on HST observations provided the best estimate of FUV flare activity, where others underestimated the emission at all ages, masses, and activity levels, by up to a factor of 104 for combined FUV continuum and line emission and greater for individual emission lines. We also confirmed previous findings that showed optically quiet low-mass stars exhibit regular FUV flares.
PubDate: Mon, 15 Jul 2024 00:00:00 GMT
DOI: 10.1093/mnras/stae1570
Issue No: Vol. 533, No. 2 (2024)
- Growth of high-redshift supermassive black holes from heavy seeds in the
BRAHMA cosmological simulations: implications of overmassive black holes-
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Pages: 1907 - 1926
Abstract: ABSTRACTJWST has revealed a large population of accreting black holes (BHs) in the early Universe. Recent work has shown that even after accounting for possible systematic biases, the high-z$M_*{\!-\!}M_{\rm \rm bh}$ relation can be above the local scaling relation by $\gt 3\sigma$. To understand the implications of these overmassive high-z BHs, we study the BH growth at $z\sim 4{\!-\!}7$ using the $[18~\mathrm{Mpc}]^3$BRAHMA cosmological simulations with systematic variations of heavy seed models that emulate direct collapse black hole (DCBH) formation. In our least restrictive seed model, we place $\sim 10^5~{\rm M}_{\odot }$ seeds in haloes with sufficient dense and metal-poor gas. To model conditions for direct collapse, we impose additional criteria based on a minimum Lyman Werner flux (LW flux $=10~J_{21}$), maximum gas spin, and an environmental richness criterion. The high-z BH growth in our simulations is merger dominated, with a relatively small contribution from gas accretion. The simulation that includes all the above seeding criteria fails to reproduce an overmassive high-z$M_*{\!-\!}M_{\rm bh}$ relation consistent with observations (by factor of $\sim 10$ at $z\sim 4$). However, more optimistic models that exclude the spin and environment based criteria are able to reproduce the observed relations if we assume $\lesssim 750~\mathrm{Myr}$ delay times between host galaxy mergers and subsequent BH mergers. Overall, our results suggest that current JWST observations may be explained with heavy seeding channels if their formation is more efficient than currently assumed DCBH conditions. Alternatively, we may need higher initial seed masses, additional contributions from lighter seeds to BH mergers, and / or more efficient modes for BH accretion.
PubDate: Sat, 27 Jul 2024 00:00:00 GMT
DOI: 10.1093/mnras/stae1819
Issue No: Vol. 533, No. 2 (2024)
- Rotational excitation and de-excitation of the interstellar propargyl
(H2CCCH+) cation by collisions with helium atoms-
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Pages: 1927 - 1937
Abstract: ABSTRACTThe propargyl cation, H2CCCH+, is a crucial hydrocarbon precursor in the chemical evolution of the interstellar medium (ISM). It serves as a key intermediate for understanding ISM hydrocarbon chemistry. This work presents state-to-state collisional rate coefficients for rotational excitation and de-excitation of ortho- and para-H2CCCH+ colliding with He at ISM-relevant temperatures (T ≤ 60 K). We employed a high-level post-Hartree-Fock CCSD(T)-F12/aug-cc-pVTZ method to generate a 3D interaction potential energy surface (3D-PES) for the weakly bound H2CCCH+-He complex. The analytical 3D-PES was then used in close-coupling calculations to determine cross-sections for rotational excitation and de-excitation of ortho- and para-H2CCCH+ by collisions with He for kinetic energies (Ek) up to 300 cm−1. Inelastic collision rate coefficients were subsequently obtained by thermally averaging the cross-sections over a Maxwell–Boltzmann distribution of kinetic energies. Our results indicate that at very low temperatures (T < 15 K), rotational transitions associated with Δj = Δkc = ±1, which are crucial for the identification of H2CCCH+ in astronomical surveys, exhibit the largest cross-sections. In contrast, at higher temperatures, transitions with Δj = Δkc = ±2 become more dominant. These data hold significant implications for the determination of the H2CCCH+ abundance in the ISM and improve the modelling of interstellar hydrocarbon-chain reaction pathways.
PubDate: Fri, 09 Aug 2024 00:00:00 GMT
DOI: 10.1093/mnras/stae1824
Issue No: Vol. 533, No. 2 (2024)
- Relative alignments between magnetic fields, velocity gradients, and dust
emission gradients in NGC 1333-
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Pages: 1938 - 1959
Abstract: ABSTRACTMagnetic fields play an important role in shaping and regulating star formation in molecular clouds. Here, we present one of the first studies examining the relative orientations between magnetic (B) fields and the dust emission, gas column density, and velocity centroid gradients on the 0.02 pc (core) scales, using the BISTRO and VLA+GBT observations of the NGC 1333 star-forming clump. We quantified these relative orientations using the Project Rayleigh Statistic (PRS) and found preferential global parallel alignment between the B field and dust emission gradients, consistent with large-scale studies with Planck. No preferential global alignments, however, are found between the B field and velocity gradients. Local PRS calculated for subregions defined by either dust emission or velocity coherence further revealed that the B field does not preferentially align with dust emission gradients in most emission-defined subregions, except in the warmest ones. The velocity-coherent structures, on the other hand, also showed no preferred B field alignments with velocity gradients, except for one potentially bubble-compressed region. Interestingly, the velocity gradient magnitude in NGC 1333 ubiquitously features prominent ripple-like structures that are indicative of magnetohydrodynamic (MHD) waves. Finally, we found B field alignments with the emission gradients to correlate with dust temperature and anticorrelate with column density, velocity dispersion, and velocity gradient magnitude. The latter two anticorrelations suggest that alignments between gas structures and B fields can be perturbed by physical processes that elevate velocity dispersion and velocity gradients, such as infall, accretions, and MHD waves.
PubDate: Wed, 31 Jul 2024 00:00:00 GMT
DOI: 10.1093/mnras/stae1829
Issue No: Vol. 533, No. 2 (2024)
- CSST strong lensing preparation: forecasting the galaxy–galaxy strong
lensing population for the China space station telescope-
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Pages: 1960 - 1975
Abstract: ABSTRACTGalaxy–galaxy strong gravitational lensing (GGSL) is a powerful probe for the formation and evolution of galaxies and cosmology, while the sample size of GGSLs leads to considerable uncertainties and potential bias. The China Space Station Telescope (CSST, to be launched in late 2026) will conduct observations across 17 500 square degrees of the sky, capturing images in the $ugriz$ bands with a spatial resolution comparable to that of the Hubble Space Telescope. We ran a set of Monte Carlo simulations to predict that the CSST’s wide-field survey will observe $\sim$160 000 galaxy–galaxy strong lenses over its lifespan, increasing the number of existing galaxy–galaxy strong lens samples by three orders of magnitude. This is comparable to the capabilities of the $\it Euclid$ telescope but with the added benefit of additional colour information. Specifically, the CSST can detect strong lenses with Einstein radii about $0.64\pm 0.42 ^{\prime \prime }$, corresponding to the velocity dispersions of $217.19 \pm 50.55 \, \text{km/s}$. These lenses exhibit a median magnification of $\sim$5. The apparent magnitude of the unlensed sources in the g band is $25.87 \pm 1.19$. The signal-to-noise ratio of the lensed images covers a range of ${\sim} 20$ to ${\sim} 1000$, allowing us to determine the Einstein radius with an accuracy ranging from ${\sim} 1~{{\ \rm per\ cent}}$ to ${\sim} 0.1~{{\ \rm per\ cent}}$, ignoring various modelling systematics. Our estimates indicate that CSST can observe rare systems like double source-plane and spiral galaxy lenses. The above selection functions of the CSST strong lensing observation help optimize the strategy of finding and modelling GGSLs.
PubDate: Tue, 20 Aug 2024 00:00:00 GMT
DOI: 10.1093/mnras/stae1865
Issue No: Vol. 533, No. 2 (2024)
- FNet II: spectral classification of quasars, galaxies, stars, and broad
absorption line (BAL) quasars-
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Pages: 1976 - 1985
Abstract: ABSTRACTIn this work, we enhance the FNet, a 1D convolutional neural network (CNN) with a residual neural network (ResNet) architecture, to perform spectral classification of quasars, galaxies, stars, and broad absorption line (BAL)-quasars in the SDSS-IV catalogue from DR17 of eBOSS. Leveraging its convolutional layers and the ResNet structure with different kernel sizes, FNet autonomously identifies various patterns within the entire sample of spectra. Since FNet does not require the intermediate step of identifying specific lines, a simple modification enabled our current network to classify all SDSS spectra. This modification involves changing the final output layer from a single value (redshift) to multiple values (probabilities of all classes), and accordingly adjusting the loss function from mean squared error to cross-entropy. FNet achieves a completeness of 99.00 per cent $\pm$ 0.20 for galaxies, 98.50 per cent $\pm$ 0.30 for quasars, 99.00 per cent $\pm$ 0.18 for BAL-quasars, and 98.80 per cent $\pm$ 0.20 for stars. These results are comparable to those obtained using QuasarNET, a standard CNN employed in the SDSS routine, comprises convolutional layers without the ResNet structure with equal kernel sizes, and is utilized for redshift measurement and classification by identifying seven emission lines. QuasarNET, in order to overcome the problem of finding a C iv emission line with broad absorption which is slightly more challenging than that of detecting emission lines requires to add BAL C iv line to the list of lines that the network learns to identify. However, this procedure is not necessary in FNet as it learns the features through a self-learning procedure.
PubDate: Tue, 06 Aug 2024 00:00:00 GMT
DOI: 10.1093/mnras/stae1878
Issue No: Vol. 533, No. 2 (2024)
- Approximate analytical solutions of the homologous collapse’s radial
evolution in time-
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Pages: 1986 - 1990
Abstract: ABSTRACTThe homologous collapse of a uniform density sphere under its self-gravity is a well-known model in cosmological studies. In the analytical integration, the evolution of the radius of the sphere is defined in terms of a parameter that is related to the physical time through a transcendental equation. The aim of this note is to construct new approximate solutions of this transcendental equation. After close examination of the piecewise Padé approximation introduced in a recent paper by Zhou and collaborators, several modifications that improve the accuracy of this approximation with the same computational cost are proposed. This new approximation shows that the use of piecewise Hermite interpolation leads to approximate solutions with continuity and much higher accuracy than Padé interpolants. Numerical experiments that confirm the above results are also presented.
PubDate: Tue, 06 Aug 2024 00:00:00 GMT
DOI: 10.1093/mnras/stae1904
Issue No: Vol. 533, No. 2 (2024)
- OGLE-2015-BLG-0845L: a low-mass M dwarf from the microlensing parallax and
xallarap effects-
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Pages: 1991 - 2004
Abstract: ABSTRACTWe present the analysis of the microlensing event OGLE-2015-BLG-0845, which was affected by both the microlensing parallax and xallarap effects. The former was detected via the simultaneous observations from the ground and Spitzer, and the latter was caused by the orbital motion of the source star in a relatively close binary. The combination of these two effects led to a mass measurement of the lens object, revealing a low-mass ($0.14 \pm 0.05 \, \mathrm{ M}_{\odot }$) M dwarf at the bulge distance ($7.6 \pm 1.0$ kpc). The source binary consists of a late F-type subgiant and a K-type dwarf of $\sim 1.2$ and $\sim 0.9 \mathrm{ M}_{\odot }$, respectively, and the orbital period is $70 \pm 10$ d. OGLE-2015-BLG-0845 is the first single-lens event in which the lens mass is measured via the binarity of the source. Given the abundance of binary systems as potential microlensing sources, the xallarap effect may not be a rare phenomenon. Our work thus highlights the application of the xallarap effect in the mass determination of microlenses, and the same method can be used to identify isolated dark lenses.
PubDate: Wed, 07 Aug 2024 00:00:00 GMT
DOI: 10.1093/mnras/stae1906
Issue No: Vol. 533, No. 2 (2024)
- SCOTCH – search for clandestine optically thick compact H ii
regions: II-
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Pages: 2005 - 2025
Abstract: ABSTRACTIn this study we present 18$-$24 GHz and high-angular-resolution (0.5 arcsec) radio wavelength Australia Telescope Compact Array follow-up observations towards a sample of 39 HC H ii region candidates. These objects, taken from a sample hosting 6.7 GHz methanol masers, were chosen due to the compact and optically thick nature of their continuum emission. We have detected 27 compact radio sources and constructed their spectral energy distributions over the 5–24 GHz range to determine the young H ii region’s physical properties, i.e. diameter, electron density ${\it n}_{\mbox{e}}$, emission measure, Lyman continuum flux ${\it N}_{\mbox{Ly}}$, and turnover frequency ${\nu }_{\mbox{t}}$. The flux measurements are fitted for 20 objects assuming an ionization-bounded H ii region with uniform density model. For the remaining seven objects that lack constraints spanning both their optically thick and thin regimes, we utilize relations from the literature to determine their physical properties. Comparing these determined parameters with those of known hypercompact (HC) and ultracompact (UC) H ii regions, we have identified 13 HC H ii regions, six intermediate objects that fall between HC H ii and UC H ii regions, six UC H ii regions and one radio jet candidate which increases the known population of HC H ii regions by $\sim$50 per cent. All the young and compact H ii regions are embedded in dusty and dense clumps and $\sim$80 per cent of the HC H ii regions identified in this work are associated with various maser species (CH$_3$OH, H$_2$O, and OH). Four of our radio sources remain optically thick at 24 GHz; we consider these to be among the youngest HC H ii regions.
PubDate: Wed, 07 Aug 2024 00:00:00 GMT
DOI: 10.1093/mnras/stae1910
Issue No: Vol. 533, No. 2 (2024)
- SDSS-IV MaNGA: stellar rotational support in disc galaxies versus central
surface density and stellar population age-
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Pages: 2026 - 2047
Abstract: ABSTRACTWe investigate how the stellar rotational support changes as a function of spatially resolved stellar population age ($D_n4000$) and relative central stellar surface density ($\Delta \Sigma _1$) for MaNGA isolated/central disc galaxies. We find that the galaxy rotational support indicator $\lambda _{R_\mathrm{e}}$ varies smoothly as a function of $\Delta \Sigma _1$ and $D_n4000$. $D_n4000$ versus $\Delta \Sigma _1$ follows a ‘J-shape’, with $\lambda _{R_\mathrm{e}}$ contributing to the scatters. In this ‘J-shaped’ pattern rotational support increases with central $D_n4000$ when $\Delta \Sigma _1$ is low but decreases with $\Delta \Sigma _1$ when $\Delta \Sigma _1$ is high. Restricting attention to low-$\Delta \Sigma _1$ (i.e. large-radius) galaxies, we suggest that the trend of increasing rotational support with $D_n4000$ for these objects is produced by a mix of two different processes, a primary trend characterized by growth in $\lambda _{R_\mathrm{e}}$ along with mass through gas accretion, on top of which disturbance episodes are overlaid, which reduce rotational support and trigger increased star formation. An additional finding is that star-forming galaxies with low $\Delta \Sigma _1$ have relatively larger radii than galaxies with higher $\Delta \Sigma _1$ at fixed stellar mass. Assuming that these relative radii rankings are preserved while galaxies are star forming then implies clear evolutionary paths in central $D_n4000$ versus $\Delta \Sigma _1$. The paper closes with comments on the implications that these paths have for the evolution of pseudo-bulges versus classical bulges. The utility of using $\rm D_n4000$–$\Delta \Sigma _1$ to study $\lambda _{R_\mathrm{e}}$ reinforces the notion that galaxy kinematics correlate both with structure and with stellar-population state, and indicates the importance of a multidimensional description for understanding bulge and galaxy evolution.
PubDate: Mon, 12 Aug 2024 00:00:00 GMT
DOI: 10.1093/mnras/stae1939
Issue No: Vol. 533, No. 2 (2024)
- Photoionization of hydrogen halides using the r-matrix method
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Pages: 2048 - 2057
Abstract: ABSTRACTIn this study, we use the UK Molecular r-matrix (ukrmol) codes in the close-coupling approximation to examine the photoionization of hydrogen halides (hydrogen fluoride, hydrogen chloride, and hydrogen bromide). This article reports the total and partial photoionization cross-sections for the $\mathrm{X}^2 \Pi$, $\mathrm{A}^2 \Sigma ^{+}$, and $\mathrm{B}^2 \Sigma ^{+}$ ionic states of these halides. The calculated cross-sections are compared with the available literature, which does not accurately represent the effective cross-sections near the threshold region, which is dominated by the Rydberg series autoionization resonances converging to the $\mathrm{A}^2 \Sigma ^{+}$ ionic state. There seems to have been minimal effort to investigate the Rydberg-bound states of these halides. Meanwhile, the r-matrix approaches have traditionally excelled at characterizing such studies. This indicates the effectiveness of this method for molecular photoionization as well as for understanding the resonant contribution to the photoionization cross-sections. The detailed cross-sections calculated comprise the complex autoionizing resonance structures capable of significantly contributing to the computations of total photoionization rates, which are necessary to maintain a steady state of ionization in astrophysical plasmas. Comparisons with the experimental measurements and the theoretical data generally show reasonable agreement across the reported energy range.
PubDate: Mon, 12 Aug 2024 00:00:00 GMT
DOI: 10.1093/mnras/stae1944
Issue No: Vol. 533, No. 2 (2024)
- Empirical instability strip for pre-He WD in EL CVn type binary
systems-
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Pages: 2058 - 2072
Abstract: ABSTRACTWe present the Transiting Exoplanet Survey Satellite (TESS) photometry and high-resolution spectra of the EL CVn-type systems, which consists of an A/F-type main-sequence (MS) star and a hotter low-mass helium white dwarf precursor (pre-He WD). In the spectral analysis, double-lined radial velocities (RVs) were obtained for the first time. From a simultaneous analysis of the TESS light and RV curves, the masses, radii, and temperatures of each component were determined. We applied multiple frequency analyses to the residual light curve after subtracting the binarity effects and detected independent frequencies. We found that the low-frequency region’s frequencies resembled those of $\delta$ Sct-type stars, while the high-frequency region’s frequencies (100–300 d$^{-1}$) likely correspond to pre-He WD components. According to our research, we found that in nine systems, the primary star with higher mass showed pulsation characteristics similar to a $\delta$-Sct-type. In only three systems, the hotter secondary components consisted of a pre-He WD with high-frequency pulsations. We examine the purity of pre-He WD instability strip by studying several EL CVn-type systems. Additionally, we propose new boundaries for the empirical instability strips of pre-He WDs.
PubDate: Tue, 13 Aug 2024 00:00:00 GMT
DOI: 10.1093/mnras/stae1948
Issue No: Vol. 533, No. 2 (2024)
- The Dark Energy Survey 5-yr photometrically classified type Ia supernovae
without host-galaxy redshifts-
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Pages: 2073 - 2088
Abstract: ABSTRACTCurrent and future Type Ia Supernova (SN Ia) surveys will need to adopt new approaches to classifying SNe and obtaining their redshifts without spectra if they wish to reach their full potential. We present here a novel approach that uses only photometry to identify SNe Ia in the 5-yr Dark Energy Survey (DES) data set using the SuperNNova classifier. Our approach, which does not rely on any information from the SN host-galaxy, recovers SNe Ia that might otherwise be lost due to a lack of an identifiable host. We select $2{,}298$ high-quality SNe Ia from the DES 5-yr data set an almost complete sample of detected SNe Ia. More than 700 of these have no spectroscopic host redshift and are potentially new SNIa compared to the DES-SN5YR cosmology analysis. To analyse these SNe Ia, we derive their redshifts and properties using only their light curves with a modified version of the SALT2 light-curve fitter. Compared to other DES SN Ia samples with spectroscopic redshifts, our new sample has in average higher redshift, bluer and broader light curves, and fainter host-galaxies. Future surveys such as LSST will also face an additional challenge, the scarcity of spectroscopic resources for follow-up. When applying our novel method to DES data, we reduce the need for follow-up by a factor of four and three for host-galaxy and live SN, respectively, compared to earlier approaches. Our novel method thus leads to better optimization of spectroscopic resources for follow-up.
PubDate: Tue, 13 Aug 2024 00:00:00 GMT
DOI: 10.1093/mnras/stae1953
Issue No: Vol. 533, No. 2 (2024)
- Metallicities for globular clusters in the fornax, sagittarius, and canis
major dwarf spheroidal galaxies and their total luminosities-
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Pages: 2089 - 2095
Abstract: ABSTRACTWe present [Fe/H] values for globular clusters associated with the Fornax, Sagittarius, and Canis Major dwarf spheroidal galaxies based on the light curve properties of their ab-type RR Lyrae variables. Fornax is a classical dwarf spheroidal containing five globular clusters and exhibiting a spheroidal shape in the sky. Sagittarius and Canis Major, possess six and four globular clusters, respectively, and have both been tidally disrupted to a significant degree by the gravitational field of the Milky Way galaxy. Based on an analysis of the periods and light curve amplitudes of 76 globular cluster ab-type RR Lyraes in Fornax, 103 in Sagittarius, and 29 in Canis Major, we find mean metallicities of $\langle$[Fe/H]$\rangle$ = –1.67 ± 0.05, –1.76 ± 0.12, and –1.69 ± 0.25 for the globular clusters in Fornax, Sagittarius, and Canis Major, respectively. Given the similarity of these three values, and coupled with the well-established correlation between the mean metal abundance and total luminosity for dwarf spheroidal galaxies, we conclude that the absolute V-band magnitudes of these three galaxies are indistinguishable to within ∼0.8 mag.
PubDate: Tue, 13 Aug 2024 00:00:00 GMT
DOI: 10.1093/mnras/stae1963
Issue No: Vol. 533, No. 2 (2024)
- Impact of nuclear matter properties on the nucleosynthesis and the
kilonova from binary neutron star merger ejecta-
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Pages: 2096 - 2112
Abstract: ABSTRACTMaterial expelled from binary neutron star (BNS) mergers can harbour r-process nucleosynthesis and power a kilonova (KN), both intimately related to the astrophysical conditions of the ejection. In turn such conditions indirectly depend on the equation of state (EOS) describing matter inside the neutron star. Therefore, in principle the above observables can hold valuable information on nuclear matter, as the merger gravitational wave signal already does. In this work, we consider the outcome of a set of BNS merger simulations employing different finite-temperature nuclear EOSs. The latter are obtained from a Skyrme-type interaction model where nuclear properties, such as the incompressibility and the nucleon effective mass at saturation density, are systematically varied. We post-process the ejecta using a reaction network coupled with a semi-analytic KN model, to assess the sensitivity on the input EOS of the final yields and the KN light curves. Both of them are found to be non-trivially influenced by the EOS, with the overall outcome being dominated by the heterogeneous outflows from the remnant disc, hosting a variable degree of neutron-rich material. The dynamical ejecta can be more directly related to the EOS parameters considered; however, we find their role in the yields production and the KN emission too entangled with the other ejecta components, in order to infer solid correlations. This result highlights the strong degeneracy that intervenes between the merger outcome and the behaviour of the intrinsic nuclear matter, and places itself as a limit to the employment of EOS-constraining approaches of such kind.
PubDate: Tue, 20 Aug 2024 00:00:00 GMT
DOI: 10.1093/mnras/stae1979
Issue No: Vol. 533, No. 2 (2024)
- Kilonova Seekers: the GOTO project for real-time citizen science in
time-domain astrophysics-
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Pages: 2113 - 2132
Abstract: ABSTRACTTime-domain astrophysics continues to grow rapidly, with the inception of new surveys drastically increasing data volumes. Democratized, distributed approaches to training sets for machine learning classifiers are crucial to make the most of this torrent of discovery – with citizen science approaches proving effective at meeting these requirements. In this paper, we describe the creation of and the initial results from the Kilonova Seekers citizen science project, built to find transient phenomena from the GOTO telescopes in near real-time. Kilonova Seekers launched in 2023 July and received over 600 000 classifications from approximately 2000 volunteers over the course of the LIGO-Virgo-KAGRA O4a observing run. During this time, the project has yielded 20 discoveries, generated a ‘gold-standard’ training set of 17 682 detections for augmenting deep-learned classifiers, and measured the performance and biases of Zooniverse volunteers on real-bogus classification. This project will continue throughout the lifetime of GOTO, pushing candidates at ever-greater cadence, and directly facilitate the next-generation classification algorithms currently in development.
PubDate: Tue, 27 Aug 2024 00:00:00 GMT
DOI: 10.1093/mnras/stae1817
Issue No: Vol. 533, No. 2 (2024)
- Beyond the Rotational Deathline: Radio Emission from Ultra-long Period
Magnetars-
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Pages: 2133 - 2155
Abstract: ABSTRACTMotivated by the recent detection of ultralong-period radio transients, we investigate new models of coherent radio emission via low-altitude electron–positron pair production in neutron stars (NSs) beyond rotationally powered curvature radiation deathlines. We find that plastic motion (akin to ‘continental drift’) and qualitatively similar thermoelectric action by temperature gradients in the crusts of slowly rotating, highly magnetized NSs could impart mild local magnetospheric twists. Regardless of which mechanism drives twists, we find that particle acceleration initiates pair cascades across charge-starved gaps above a mild critical twist. Cascades are initiated via resonant inverse-Compton scattered photons or curvature radiation, and may produce broad-band coherent radio emission. We compute the pair luminosity (maximum allowed radio luminosity) for these two channels, and derive deathlines and ‘active zones’ in $P-\dot{P}$ space from a variety of considerations. We find these twist-initiated pair cascades only occur for magnetar-like field strengths $B \gtrsim 10^{14}$ G and long periods: $P_{\rm RICS} \gtrsim 120 \,\, (T/10^{6.5} {\rm K})^{-5} \, {\rm s}$ and $P_{\rm curv} \gtrsim 150 \,\, ({\rm v_{\rm pl}}/10^{3} {\, \rm cm \, yr^{-1}})^{-7/6} \, {\rm s}$. Using a simplified geometric model, we find that plastic motion or thermoelectrically driven twists might naturally reproduce the observed luminosities, time-scales, and timing signatures. We further derive ‘active zones’ in which rotationally powered pair creation occurs via resonantly scattered photons, beyond standard curvature deathlines for pulsars. All cascades are generically accompanied by simultaneous (non-)thermal X-ray/UV counterparts which might be detectable with current instrumentation.
PubDate: Fri, 09 Aug 2024 00:00:00 GMT
DOI: 10.1093/mnras/stae1813
Issue No: Vol. 533, No. 2 (2024)
- Redshift constrain of BL Lac PKS 1424+240
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Pages: 2156 - 2161
Abstract: ABSTRACTIn the period between 2009 and 2015, several very high-energy (VHE $> 100$ GeV) gamma-ray flaring events from the BL Lac object PKS 1424+240 were observed by the Cerenkov telescopes VERITAS and MAGIC. It had uncertain redshift (z) and using spectroscopical measurement, Paiano et al. (2017) found it to be $z=0.604$. Using four different extragalactic background light (EBL) models and the photohadronic model, nine independently observed VHE gamma-ray spectra of PKS 1424+240 are analysed and a global $\chi ^2$ fit is performed on all observations to estimate the best-fitting value for the redshift for each EBL model. Confidence levels (CL) intervals for the redshift are also estimated using all the EBL models. This method is tested by comparing our analysis with the observed value. It is shown that the photohadronic scenario provides an excellent description of all the observed spectra. It is found that the EBL model of Dominguez et al. (2011) is the one that provides the most restrictive limits on the redshift of PKS 1424+240, but in our analysis, $z=0.604$ lies within the $3\sigma$ CL interval of the EBL model of Saldana-Lopez et al. (2021).
PubDate: Wed, 31 Jul 2024 00:00:00 GMT
DOI: 10.1093/mnras/stae1847
Issue No: Vol. 533, No. 2 (2024)
- tessilator: a one-stop shop for measuring TESS rotation periods
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Pages: 2162 - 2184
Abstract: ABSTRACTWe present a software package designed to produce photometric light curves and measure rotation periods from full-frame images taken by the Transiting Exoplanet Survey Satellite (TESS), which we name ‘tessilator’. tessilator is the only publicly available code that will run a full light curve and rotation period ($P_{\rm rot}$) analysis based on just a (list of) target identifier(s) or sky position(s) via a simple command-line prompt. This paper sets out to introduce the rationale for developing tessilator, and then describes the methods, considerations, and assumptions for: extracting photometry; dealing with potential contamination; accounting for natural and instrumental systematic effects; light-curve normalization and detrending; removing outliers and unreliable data; and finally, measuring the $P_{\rm rot}$ value and several periodogram attributes. Our methods have been tuned specifically to optimize TESS light curves and are independent from the pipelines developed by the TESS Science Processing Operations Center (SPOC), meaning tessilator can, in principle, analyse any target across the entire celestial sphere. We compare tessilator$P_{\rm rot}$ measurements with TESS-SPOC-derived light curves of 1560 (mainly solar-type and low-mass) stars across four benchmark open clusters (Pisces–Eridanus, the Pleiades, the Hyades, and Praesepe) and a sample of nearby field M-dwarfs. From a vetted subsample of 864 targets we find an excellent return of $P_{\rm rot}$ matches for the first three open clusters ($\gt 85$ per cent) and a moderate ($\sim 60$ per cent) match for the 700 Myr Praesepe and MEarth sample, which validates tessilator as a tool for measuring $P_{\rm rot}$. The tessilator code is available at https://github.com/alexbinks/tessilator.
PubDate: Wed, 31 Jul 2024 00:00:00 GMT
DOI: 10.1093/mnras/stae1850
Issue No: Vol. 533, No. 2 (2024)
- Jupiter's Hotspots as observed by JIRAM-Juno: limb darkening in thermal
infrared-
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Pages: 2185 - 2198
Abstract: ABSTRACTThe Jupiter InfraRed Auroral Mapper (JIRAM) instrument onboard the Juno spacecraft performed repeated observations of Jupiter's North Equatorial Belt (NEB) around the time of 12th Juno pericenter passage on 2018 April 1. The data consist of thermal infrared images and show, among other atmospheric features, two bright Hotspots on the boundary between the NEB and the Equatorial Zone. Night-time images of the same areas at different emission angles were used to constrain the trend of the limb-darkening function. Comparison with simulated observations, computed for different emission angles, total opacities, single scattering albedo ω0, and asymmetry parameter g suggests that ω0 ∼ 0.90 ± 0.05 and g ∼ 0.37 ± 0.15 provide best match with data. Subsequently, we computed the ω0 and g resulting from different size distributions, taking into account the complex refractive indices of ammonium hydrosulfide (NH4SH) by Howett et al. [2007] and Ferraro et al. [1980]. Only the former data set is marginally consistent with JIRAM observations. Similarly, ammonia and hydrazine barely reproduce the experimental data. Tholin, although not usually considered a realistic component for Jupiter's aerosols, provides a better match for particle radii between 0.7 and 1 μm, both as a pure material as well as a thick coating over NH4SH cores. Notably, this radius range is consistent with the mean radius of aerosols as estimated by Ragent et al. [1998] on the basis of Galileo entry probe data. Comparison with literature suggests that similar results can be achieved by a large variety of contaminants bearing C–N bounds.
PubDate: Thu, 01 Aug 2024 00:00:00 GMT
DOI: 10.1093/mnras/stae1858
Issue No: Vol. 533, No. 2 (2024)
- The application of machine learning in tidal evolution simulation of
star–planet systems-
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Pages: 2199 - 2212
Abstract: ABSTRACTWith the release of a large amount of astronomical data, an increasing number of close-in hot Jupiters have been discovered. Calculating their evolutionary curves using star–planet interaction models presents a challenge. To expedite the generation of evolutionary curves for these close-in hot Jupiter systems, we utilized tidal interaction models established on mesa to create 15 745 samples of star–planet systems and 7500 samples of stars. Additionally, we employed a neural network (Multilayer Perceptron – MLP) to predict the evolutionary curves of the systems, including stellar effective temperature, radius, stellar rotation period, and planetary orbital period. The median relative errors of the predicted evolutionary curves were found to be 0.15 per cent, 0.43 per cent, 2.61 per cent, and 0.57 per cent, respectively. Furthermore, the speed at which we generate evolutionary curves exceeds that of model-generated curves by more than four orders of magnitude. We also extracted features of planetary migration states and utilized lightgbm to classify the samples into six categories for prediction. We found that by combining three types that undergo long-term double synchronization into one label, the classifier effectively recognized these features. Apart from systems experiencing long-term double synchronization, the median relative errors of the predicted evolutionary curves were all below 4 per cent. Our work provides an efficient method to save significant computational resources and time with minimal loss in accuracy. This research also lays the foundation for analysing the evolutionary characteristics of systems under different migration states, aiding in the understanding of the underlying physical mechanisms of such systems. Finally, to a large extent, our approach could replace the calculations of theoretical models.
PubDate: Tue, 06 Aug 2024 00:00:00 GMT
DOI: 10.1093/mnras/stae1870
Issue No: Vol. 533, No. 2 (2024)
- A comparative study of radio signatures from winds and jets: modelling
synchrotron emission and polarization-
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Pages: 2213 - 2231
Abstract: ABSTRACTOutflows driven by active galactic nuclei (AGNs) are seen in numerous compact sources; however, it has remained unclear how to distinguish between the driving mechanisms, such as winds and jets. Therefore, our study aims to offer observational insights from simulations to aid in this distinction. Specifically, in this paper, we investigate the evolution of wide-angled moderately relativistic magnetized winds and analyse their non-thermal radio emission and polarization properties. We find that the evolution of winds varies depending on factors such as power, density, and opening angle, which in turn influence their observable characteristics. Additionally, different viewing angles can lead to varying observations. Furthermore, we note distinctions in the evolution of winds compared to jets, resulting in disparities in their observable features. Jets typically exhibit a thin spine and hotspot(s). Winds manifest broader spines or an ‘hourglass-shaped’ bright emission in the cocoon, which are capped by bright arcs. Both display high polarization coinciding with the bright spine and hotspots/arcs, although these regions are relatively compact and localized in jets when compared to winds. We emphasize the importance of high resolution, as we demonstrate that emission features from both jets and winds can become indistinguishable at lower resolutions. The distribution of polarization is largely unaffected by resolution, though lower polarization becomes more noticeable when the resolution is decreased.
PubDate: Mon, 05 Aug 2024 00:00:00 GMT
DOI: 10.1093/mnras/stae1890
Issue No: Vol. 533, No. 2 (2024)
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