Subjects -> ASTRONOMY (Total: 94 journals)
Showing 1 - 46 of 46 Journals sorted alphabetically
Advances in Astronomy     Open Access   (Followers: 49)
Annual Review of Astronomy and Astrophysics     Full-text available via subscription   (Followers: 50)
Annual Review of Earth and Planetary Sciences     Full-text available via subscription   (Followers: 67)
Artificial Satellites     Open Access   (Followers: 21)
Astrobiology     Hybrid Journal   (Followers: 11)
Astronomical & Astrophysical Transactions: The Journal of the Eurasian Astronomical Society     Hybrid Journal   (Followers: 7)
Astronomical Review     Open Access   (Followers: 5)
Astronomische Nachrichten     Hybrid Journal   (Followers: 4)
Astronomy & Geophysics     Hybrid Journal   (Followers: 49)
Astronomy and Astrophysics     Full-text available via subscription   (Followers: 67)
Astronomy and Computing     Hybrid Journal   (Followers: 6)
Astronomy Letters     Hybrid Journal   (Followers: 22)
Astronomy Reports     Hybrid Journal   (Followers: 22)
Astronomy Studies Development     Open Access   (Followers: 15)
Astroparticle Physics     Hybrid Journal   (Followers: 10)
Astrophysical Bulletin     Hybrid Journal   (Followers: 4)
Astrophysics     Hybrid Journal   (Followers: 35)
Astrophysics and Space Science     Hybrid Journal   (Followers: 49)
Astrophysics and Space Sciences Transactions (ASTRA)     Open Access   (Followers: 60)
Astropolitics: The International Journal of Space Politics & Policy     Hybrid Journal   (Followers: 13)
Celestial Mechanics and Dynamical Astronomy     Hybrid Journal   (Followers: 15)
Chinese Astronomy and Astrophysics     Full-text available via subscription   (Followers: 25)
Colloid Journal     Hybrid Journal   (Followers: 2)
Comptes Rendus : Physique     Open Access   (Followers: 2)
Computational Astrophysics and Cosmology     Open Access   (Followers: 6)
Earth and Planetary Science Letters     Hybrid Journal   (Followers: 143)
Earth, Moon, and Planets     Hybrid Journal   (Followers: 47)
Earth, Planets and Space     Open Access   (Followers: 77)
EAS Publications Series     Full-text available via subscription   (Followers: 8)
EPL Europhysics Letters     Partially Free   (Followers: 8)
Experimental Astronomy     Hybrid Journal   (Followers: 38)
Expert Opinion on Astronomy and Astrophysics     Open Access   (Followers: 8)
Extreme Life, Biospeology & Astrobiology - International Journal of the Bioflux Society     Full-text available via subscription   (Followers: 4)
Few-Body Systems     Hybrid Journal   (Followers: 1)
Foundations of Physics     Hybrid Journal   (Followers: 40)
Frontiers in Astronomy and Space Sciences     Open Access   (Followers: 15)
Galaxies     Open Access   (Followers: 6)
Globe, The     Full-text available via subscription   (Followers: 3)
Gravitation and Cosmology     Hybrid Journal   (Followers: 6)
Icarus     Hybrid Journal   (Followers: 71)
International Journal of Advanced Astronomy     Open Access   (Followers: 21)
International Journal of Astrobiology     Hybrid Journal   (Followers: 4)
International Journal of Astronomy     Open Access   (Followers: 22)
International Journal of Astronomy and Astrophysics     Open Access   (Followers: 36)
International Journal of Satellite Communications Policy and Management     Hybrid Journal   (Followers: 15)
International Letters of Chemistry, Physics and Astronomy     Open Access   (Followers: 8)
ISRN Astronomy and Astrophysics     Open Access   (Followers: 14)
Journal for the History of Astronomy     Full-text available via subscription   (Followers: 20)
Journal of Astrobiology & Outreach     Open Access   (Followers: 5)
Journal of Astronomical Instrumentation     Open Access   (Followers: 3)
Journal of Astrophysics     Open Access   (Followers: 33)
Journal of Astrophysics and Astronomy     Open Access   (Followers: 58)
Journal of Atmospheric and Solar-Terrestrial Physics     Hybrid Journal   (Followers: 133)
Journal of Geophysical Research : Planets     Full-text available via subscription   (Followers: 116)
Journal of Geophysical Research : Space Physics     Full-text available via subscription   (Followers: 136)
Journal of High Energy Astrophysics     Full-text available via subscription   (Followers: 25)
Kinematics and Physics of Celestial Bodies     Hybrid Journal   (Followers: 11)
KronoScope     Hybrid Journal   (Followers: 1)
Macalester Journal of Physics and Astronomy     Open Access   (Followers: 5)
Monthly Notices of the Royal Astronomical Society     Hybrid Journal   (Followers: 13)
Monthly Notices of the Royal Astronomical Society : Letters     Hybrid Journal   (Followers: 2)
Nature Astronomy     Hybrid Journal   (Followers: 14)
New Astronomy     Hybrid Journal   (Followers: 26)
New Astronomy Reviews     Full-text available via subscription   (Followers: 19)
Nonlinear Dynamics     Hybrid Journal   (Followers: 19)
NRIAG Journal of Astronomy and Geophysics     Open Access   (Followers: 4)
Physics of the Dark Universe     Open Access   (Followers: 4)
Planetary and Space Science     Hybrid Journal   (Followers: 106)
Planetary Science     Open Access   (Followers: 52)
Proceedings of the International Astronomical Union     Full-text available via subscription   (Followers: 2)
Publications of the Astronomical Society of Australia     Hybrid Journal   (Followers: 3)
Publications of the Astronomical Society of Japan     Hybrid Journal   (Followers: 4)
Research & Reviews : Journal of Space Science & Technology     Full-text available via subscription   (Followers: 20)
Research in Astronomy and Astrophysics     Full-text available via subscription   (Followers: 38)
Revista Mexicana de Astronomía y Astrofísica     Open Access   (Followers: 3)
Science China : Physics, Mechanics & Astronomy     Full-text available via subscription   (Followers: 4)
Science China Physics, Mechanics & Astronomy     Hybrid Journal   (Followers: 4)
Solar Physics     Hybrid Journal   (Followers: 29)
Solar System Research     Hybrid Journal   (Followers: 15)
Space Science International     Open Access   (Followers: 118)
Space Science Reviews     Hybrid Journal   (Followers: 92)
Space Weather     Full-text available via subscription   (Followers: 27)
Transport and Aerospace Engineering     Open Access   (Followers: 13)
Universe     Open Access   (Followers: 6)
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Publications of the Astronomical Society of Australia
Journal Prestige (SJR): 1.237
Citation Impact (citeScore): 2
Number of Followers: 3  
 
  Hybrid Journal Hybrid journal (It can contain Open Access articles)
ISSN (Print) 1323-3580 - ISSN (Online) 1448-6083
Published by Cambridge University Press Homepage  [353 journals]
  • Variational inference as an alternative to MCMC for parameter estimation
           and model selection

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      Authors: Gunapati; Geetakrishnasai, Jain, Anirudh, Srijith, P. K., Desai, Shantanu
      First page: 1
      Abstract: Most applications of Bayesian Inference for parameter estimation and model selection in astrophysics involve the use of Monte Carlo techniques such as Markov Chain Monte Carlo (MCMC) and nested sampling. However, these techniques are time-consuming and their convergence to the posterior could be difficult to determine. In this study, we advocate variational inference as an alternative to solve the above problems, and demonstrate its usefulness for parameter estimation and model selection in astrophysics. Variational inference converts the inference problem into an optimisation problem by approximating the posterior from a known family of distributions and using Kullback–Leibler divergence to characterise the difference. It takes advantage of fast optimisation techniques, which make it ideal to deal with large datasets and makes it trivial to parallelise on a multicore platform. We also derive a new approximate evidence estimation based on variational posterior, and importance sampling technique called posterior-weighted importance sampling for the calculation of evidence, which is useful to perform Bayesian model selection. As a proof of principle, we apply variational inference to five different problems in astrophysics, where Monte Carlo techniques were previously used. These include assessment of significance of annual modulation in the COSINE-100 dark matter experiment, measuring exoplanet orbital parameters from radial velocity data, tests of periodicities in measurements of Newton’s constant G, assessing the significance of a turnover in the spectral lag data of GRB 160625B, and estimating the mass of a galaxy cluster using weak gravitational lensing. We find that variational inference is much faster than MCMC and nested sampling techniques for most of these problems while providing competitive results. All our analysis codes have been made publicly available.
      PubDate: 2022-01-25
      DOI: 10.1017/pasa.2021.64
       
  • Massive high-redshift quiescent galaxies with JWST

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      Authors: Nanayakkara; Themiya, Esdaile, James, Glazebrook, Karl, Espejo Salcedo, Juan M., Durre, Mark, Jacobs, Colin
      First page: 2
      Abstract: Recent ground-based deep observations of the Universe have discovered large populations of massive quiescent galaxies at . With the launch of the James Webb Space Telescope (JWST), the on-board Near-Infrared Spectrograph (NIRSpec) instrument will provide continuous spectroscopic coverage of these galaxies. Here we show that NIRSpec/CLEAR spectroscopy is ideal to probe the completeness of photometrically selected massive quiescent galaxies such as the ones presented by Schreiber et al. (2018b, A&A, 618, A85). Using a subset of the Schreiber et al. (2018b, A&A, 618, A85) sample with deep Keck/MOSFIRE spectroscopy presented by Esdaile J., et al. (2021b, ApJ, 908, L35), we perform a suite of mock JWST/NIRSpec observations to determine optimal observing strategies to efficiently recover the star formation histories (SFHs), element abundances, and kinematics of these massive quiescent galaxies. We find that at , medium resolution G235M/FL170LP NIRSpec observations could recover element abundances at an accuracy of , which is comparable to local globular clusters. Mimicking ZFOURGE COSMOS photometry, we perform mock spectrophotometric fitting with Prospector to show that the overall shape of the SFHs of our mock galaxies can be recovered well, albeit with a dependency on the number of non-parametric SFH bins. We show that deep high-resolution G235H/FL170LP integral field spectroscopy with a per spaxel is required to constrain the rotational properties of our sample at confidence. Thus, through optimal grism/filter choices, JWST/NIRSpec slit and integral field spectroscopy observations would provide tight constraints to galaxy evolution in the early Universe.
      PubDate: 2022-01-26
      DOI: 10.1017/pasa.2021.61
       
  • Early-time searches for coherent radio emission from short GRBs with the
           Murchison Widefield Array

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      Authors: Tian; J., Anderson, G. E., Hancock, P. J., Miller-Jones, J. C. A., Sokolowski, M., Rowlinson, A., Williams, A., Morgan, J., Hurley-Walker, N., Kaplan, D. L., Murphy, Tara, Tingay, S. J., Johnston-Hollitt, M., Bannister, K. W., Bell, M. E., Meyers, B. W.
      First page: 3
      Abstract: Many short gamma-ray bursts (GRBs) originate from binary neutron star mergers, and there are several theories that predict the production of coherent, prompt radio signals either prior, during, or shortly following the merger, as well as persistent pulsar-like emission from the spin-down of a magnetar remnant. Here we present a low frequency (170–200 MHz) search for coherent radio emission associated with nine short GRBs detected by the Swift and/or Fermi satellites using the Murchison Widefield Array (MWA) rapid-response observing mode. The MWA began observing these events within 30–60 s of their high-energy detection, enabling us to capture any dispersion delayed signals emitted by short GRBs for a typical range of redshifts. We conducted transient searches at the GRB positions on timescales of 5 s, 30 s, and 2 min, resulting in the most constraining flux density limits on any associated transient of 0.42, 0.29, and 0.084 Jy, respectively. We also searched for dispersed signals at a temporal and spectral resolution of 0.5 s and 1.28 MHz, but none were detected. However, the fluence limit of 80–100 Jy ms derived for GRB 190627A is the most stringent to date for a short GRB. Assuming the formation of a stable magnetar for this GRB, we compared the fluence and persistent emission limits to short GRB coherent emission models, placing constraints on key parameters including the radio emission efficiency of the nearly merged neutron stars (), the fraction of magnetic energy in the GRB jet (), and the radio emission efficiency of the magnetar remnant (). Comparing the limits derived for our full GRB sample (along with those in the literature) to the same emission models, we demonstrate that our fluence limits only place weak constraints on the prompt emission predicted from the interaction between the relativistic GRB jet and the interstellar medium for a subset of magnetar parameters. However, the 30-min flux density limits were sensitive enough to theoretically detect the persistent radio emission from magnetar remnants up to a redshift of . Our non-detection of this emission could imply that some GRBs in the sample were not genuinely short or did not result from a binary neutron star merger, the GRBs were at high redshifts, these mergers formed atypical magnetars, the radiation beams of the magnetar remnants were pointing away from Earth, or the majority did not form magnetars but rather collapse directly into black holes.
      PubDate: 2022-02-03
      DOI: 10.1017/pasa.2021.58
       
  • The non-thermal emission from the colliding-wind binary Apep

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      Authors: del Palacio; S., Benaglia, P., De Becker, M., Bosch-Ramon, V., Romero, G. E.
      First page: 4
      Abstract: Therecently discovered massive binary system Apep is the most powerful synchrotron emitter among the known Galactic colliding-wind binaries. This makes this particular system of great interest to investigate stellar winds and the non-thermal processes associated with their shocks. This source was detected at various radio bands, and in addition the wind-collision region was resolved by means of very-long baseline interferometric observations. We use a non-thermal emission model for colliding-wind binaries to derive physical properties of this system. The observed morphology in the resolved maps allows us to estimate the system projection angle on the sky to be . The observed radio flux densities also allow us to characterise both the intrinsic synchrotron spectrum of the source and its modifications due to free–free absorption in the stellar winds at low frequencies; from this, we derive mass–loss rates of the stars of and . Finally, the broadband spectral energy distribution is calculated for different combinations of the remaining free parameters, namely the intensity of the magnetic field and the injected power in non-thermal particles. We show that the degeneracy of these two parameters can be solved with observations in the high-energy domain, most likely in the hard X-rays but also possibly in -rays under favourable conditions.
      PubDate: 2022-01-31
      DOI: 10.1017/pasa.2021.60
       
  • GASKAP-HI pilot survey science I: ASKAP zoom observations of Hi emission
           in the Small Magellanic Cloud

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      Authors: Pingel; N. M., Dempsey, J., McClure-Griffiths, N. M., Dickey, J. M., Jameson, K. E., Arce, H., Anglada, G., Bland-Hawthorn, J., Breen, S. L., Buckland-Willis, F., Clark, S. E., Dawson, J. R., Dénes, H., Di Teodoro, E. M., For, B.-Q., Foster, Tyler J., Gómez, J. F., Imai, H., Joncas, G., Kim, C.-G., Lee, M.-Y., Lynn, C., Leahy, D., Ma, Y. K., Marchal, A., McConnell, D., Miville-Deschènes, M.-A., Moss, V. A., Murray, C. E., Nidever, D., Peek, J., Stanimirović, S., Staveley-Smith, L., Tepper-Garcia, T., Tremblay, C. D., Uscanga, L., van Loon, J. Th., Vázquez-Semadeni, E., Allison, J. R., Anderson, C. S., Ball, Lewis, Bell, M., Bock, D. C.-J., Bunton, J., Cooray, F. R., Cornwell, T., Koribalski, B. S., Gupta, N., Hayman, D. B., Harvey-Smith, L., Lee-Waddell, K., Ng, A., Phillips, C. J., Voronkov, M., Westmeier, T., Whiting, M. T.
      First page: 5
      Abstract: We present the most sensitive and detailed view of the neutral hydrogen () emission associated with the Small Magellanic Cloud (SMC), through the combination of data from the Australian Square Kilometre Array Pathfinder (ASKAP) and Parkes (Murriyang), as part of the Galactic Australian Square Kilometre Array Pathfinder (GASKAP) pilot survey. These GASKAP-HI pilot observations, for the first time, reveal in the SMC on similar physical scales as other important tracers of the interstellar medium, such as molecular gas and dust. The resultant image cube possesses an rms noise level of 1.1 K () spectral channel with an angular resolution of (). We discuss the calibration scheme and the custom imaging pipeline that utilises a joint deconvolution approach, efficiently distributed across a computing cluster, to accurately recover the emission extending across the entire field-of-view. We provide an overview of the data products and characterise several aspects including the noise properties as a function of angular resolution and the represented spatial scales by deriving the global transfer function over the full spectral range. A preliminary spatial power spectrum analysis on individual spectral channels reveals that the power law nature of the density distribution extends down to scales of 10 pc. We highlight the scientific potential of these data by comparing the properties of an outflowing high-velocity cloud with previous ASKAP+Parkes test observations.
      PubDate: 2022-02-07
      DOI: 10.1017/pasa.2021.59
       
  • Gravitational clearing of natural satellite orbits

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      Authors: Hill; Roderick J.
      First page: 6
      Abstract: The distribution of diameters and orbital distances from the parent body of 156 named moons of the planets in the Solar System is not random. All 11 moons with diameters larger than are positioned between and 4 million km from the parent, whereas the far more numerous small moons are distributed on both sides of this central region and are largely absent from the region in between. This small-satellite ‘exclusion region’ is particularly evident for the gas giants since they have multiple satellites spanning a wide range of distances from the parent. Application of mathematical criteria analogous to those that have been used to help define the ‘gravitational clearing’ of planetary orbits around the Sun suggests that the absence of small satellites in this region around the planets may be a result (atleast in part) of gravitational clearing by the large moons present at these distances from the parent. The most significant exception to the observed diameter-distance distribution—Hyperion, on Saturn—is attributed to its 3:4 orbital resonance with Titan, while other obvious exceptions are the Trojan satellites of Saturn’s moons Tethys and Dione. The smallest satellite diameter that seems necessary for clearing of its ‘sphere of influence’ is around .
      PubDate: 2022-02-08
      DOI: 10.1017/pasa.2021.62
       
  • Multimessenger astronomy with a kHz-band gravitational-wave observatory

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      Authors: Sarin; Nikhil, Lasky, Paul D.
      First page: 7
      Abstract: Proposed next-generation networks of gravitational-wave observatories include dedicated kilohertz instruments that target neutron star science, such as the proposed Neutron Star Extreme Matter Observatory, NEMO. The original proposal for NEMO highlighted the need for it to exist in a network of gravitational-wave observatories to ensure detection confidence and sky localisation of sources. We show that NEMO-like observatories have significant utility on their own as coincident electromagnetic observations can provide the detection significance and sky localisation. We show that, with a single NEMO-like detector and expected electromagnetic observatories in the late 2020 s and early 2030 s such as the Vera C. Rubin observatory and SVOM, approximately 40% of all binary neutron star mergers detected with gravitational waves could be confidently identified as coincident multimessenger detections. We show that we expect coincident observations of gravitational-wave mergers with gamma-ray burst prompt emission, detections with kilonova observations, and with broadband afterglows and kilonovae, where the uncertainties are 90% confidence intervals arising from uncertainty in current merger-rate estimates. Combined, this implies a coincident detection rate of out to . These numbers indicate significant science potential for a single kilohertz gravitational-wave detector operating without a global network of other gravitational-wave observatories.
      PubDate: 2022-02-09
      DOI: 10.1017/pasa.2022.1
       
  • A search for technosignatures toward the Galactic Centre at 150 MHz

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      Authors: Tremblay; Chenoa D., Price, Danny C., Tingay, Steven J.
      First page: 8
      Abstract: This paper is the fourth in a series of low-frequency searches for technosignatures. Using the Murchison Widefield Array over two nights, we integrate 7 h of data toward the Galactic Centre (centred on the position of Sagittarius ) with a total field-of-view of . We present a targeted search toward 144 exoplanetary systems, at our best yet angular resolution (75 arcsec). This is the first technosignature search at a central frequency of 155 MHz toward the Galactic Centre (our previous central frequencies have been lower). A blind search toward in excess of 3 million stars toward the Galactic Centre and Galactic bulge is also completed, placing an equivalent isotropic power limit at the distance to the Galactic Centre. No plausible technosignatures are detected.
      PubDate: 2022-03-15
      DOI: 10.1017/pasa.2022.5
       
  • Understanding the impact of diffusion of CO in the astrochemical models

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      Authors: Acharyya; Kinsuk
      First page: 9
      Abstract: The mobility of lighter species on the surface of interstellar dust grains plays a crucial role in forming simple through complex molecules. Carbon monoxide is one of the most abundant molecules, its surface diffusion on the grain surface is essential to forming many molecules. Recent laboratory experiments found a diverse range of diffusion barriers for CO on the grain surface, their use can significantly impact the abundance of several molecules. The impact of different diffusion barriers of CO, in the astrochemical models, is studied to understand its effect on the abundance of solid CO and the species for which it is a reactant partner. A gas-grain network is used for three different physical conditions; cold core and warm-up models with slow and fast heating rates. Two different ratios (0.3 and 0.5) between diffusion and desorption barrier are utilised for all the species. For each physical condition and ratio, six different models are run by varying diffusion barriers of CO. Solid CO abundance for the models with the lowest diffusion barrier yields less than 0.1% of water ice for cold clouds and a maximum of 0.4% for slow and fast warm-up models. Also, solid in dense clouds is significantly overproduced ( of water). The abundance of H2CO and showed an opposite trend, and HCOOH, , , and are produced in lower quantities for models with low diffusion barriers for CO. Considerable variation in abundance is observed between models with the high and low diffusion barrier. Models with higher diffusion barriers provide a relatively better agreement with the observed abundances when compared with the models having lower diffusion barriers.
      PubDate: 2022-03-18
      DOI: 10.1017/pasa.2022.7
       
  • The First Large Absorption Survey in H i (FLASH): I. Science goals and
           survey design

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      Authors: Allison; James R., Sadler, E. M., Amaral, A. D., An, T., Curran, S. J., Darling, J., Edge, A. C., Ellison, S. L., Emig, K. L., Gaensler, B. M., Garratt-Smithson, L., Glowacki, M., Grasha, K., Koribalski, B. S., Lagos, C. del P., Lah, P., Mahony, E. K., Mao, S. A., Morganti, R., Moss, V. A., Pettini, M., Pimbblet, K. A., Power, C., Salas, P., Staveley-Smith, L., Whiting, M. T., Wong, O. I., Yoon, H., Zheng, Z., Zwaan, M. A.
      First page: 10
      Abstract: We describe the scientific goals and survey design of the First Large Absorption Survey in H i (FLASH), a wide field survey for 21-cm line absorption in neutral atomic hydrogen (H i) at intermediate cosmological redshifts. FLASH will be carried out with the Australian Square Kilometre Array Pathfinder (ASKAP) radio telescope and is planned to cover the sky south of at frequencies between 711.5 and 999.5 MHz. At redshifts between and (look-back times of 4 – 8 Gyr), the H i content of the Universe has been poorly explored due to the difficulty of carrying out radio surveys for faint 21-cm line emission and, at ultra-violet wavelengths, space-borne searches for Damped Lyman- absorption in quasar spectra. The ASKAP wide field of view and large spectral bandwidth, in combination with a radio-quiet site, will enable a search for absorption lines in the radio spectra of bright continuum sources over 80% of the sky. This survey is expected to detect at least several hundred intervening 21-cm absorbers and will produce an H i-absorption-selected catalogue of galaxies rich in cool, star-forming gas, some of which may be concealed from optical surveys. Likewise, at least several hundred associated 21-cm absorbers are expected to be detected within the host galaxies of radio sources at , providing valuable kinematical information for models of gas accretion and jet-driven feedback in radio-loud active galactic nuclei. FLASH will also detect OH 18-cm absorbers in diffuse molecular gas, megamaser OH emission, radio recombination lines, and stacked H i emission.
      PubDate: 2022-03-21
      DOI: 10.1017/pasa.2022.3
       
  • Intensity correlation functions of microwave maser sources

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      Authors: Shepelev; A. V.
      First page: 11
      Abstract: Astrophysical sources of microwave radiation with extremely high spectral brightness are interpreted as masers. But by itself, the information about high brightness of radiation does not make it possible to establish whether the radiation is thermal or maser. This can be determined only on the basis of the analysis of high-order correlation functions. A possible measurement procedure for the second-order autocorrelation function (the bunching parameter) for these sources is proposed.
      PubDate: 2022-04-04
      DOI: 10.1017/pasa.2022.11
       
  • Galaxy evolution through infrared and submillimetre spectroscopy:
           Measuring star formation and black hole accretion with JWST and ALMA

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      Authors: Mordini; Sabrina, Spinoglio, Luigi, Fernández-Ontiveros, Juan Antonio
      First page: 12
      Abstract: Rest-frame mid- to far-infrared (IR) spectroscopy is a powerful tool to study how galaxies formed and evolved, because a major part of their evolution occurs in heavily dust enshrouded environments, especially at the so-called Cosmic Noon (). Using the calibrations of IR lines and features, recently updated with Herschel and Spitzer spectroscopy, we predict their expected fluxes with the aim to measure the Star Formation (SF) and the Black Hole Accretion (BHA) rates in intermediate to high redshift galaxies. On the one hand, the recent launch of the James Webb Space Telescope (JWST) offers new mid-IR spectroscopic capabilities that will enable for the first time a detailed investigation of both the SF and the BHA obscured processes as a function of cosmic time. We make an assessment of the spectral lines and features that can be detected by JWST-MIRI in galaxies and active galactic nuclei up to redshift . The fine structure lines of [MgIV]4.49 and [ArVI]4.53 can be used as BHA rate tracers for the range, and we propose the [NeVI]7.65 line as the best tracer for . The [ArII]6.98 and [ArIII]8.99 lines can be used to measure the SF rate at and , respectively, while the stronger [NeII]12.8
      PubDate: 2022-04-01
      DOI: 10.1017/pasa.2022.10
       
  • Searching for the synchrotron cosmic web again: A replication attempt

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      Authors: Hodgson; Torrance, Johnston-Hollitt, Melanie, McKinley, Benjamin, Hurley-Walker, Natasha
      First page: 13
      Abstract: We follow up on the surprising recent announcement by Vernstrom et al. (2021, MNRAS) of the detection of the synchrotron cosmic web. We attempt to reproduce their detection with new observations with the Phase II, extended configuration of the Murchison Widefield Array at 118.5 MHz. We reproduce their detection methodology by stacking pairs of nearby luminous red galaxies (LRGs)—used as tracers for clusters and galaxy groups—contained in our low-frequency radio observations. We show that our observations are significantly more sensitive than those used in Vernstrom et al. and that our angular sensitivity is sufficient. And yet, we make no statistically significant detection of excess radio emission along the bridge spanning the LRG pairs. This non-detection is true both for the original LRG pair catalogue as used in Vernstrom et al., as well as for other larger catalogues with modified selection criteria. Finally, we return to the original data sets used in Vernstrom et al., and find that whilst we clearly reproduce the excess X-ray emission from ROSAT, we are not able to reproduce any kind of broad and extended excess intercluster filamentary emission using the original 118.5 MHz MWA survey data. In the interests of understanding this result, as part of this paper we release images of the 14 fields used in this study, the final stacked images, as well as key components of our stacking and modelling code.
      PubDate: 2022-04-04
      DOI: 10.1017/pasa.2022.9
       
  • A geometric view of closure phases in interferometry

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      Authors: Thyagarajan; Nithyanandan, Carilli, Chris L.
      First page: 14
      Abstract: Closure phase is the phase of a closed-loop product of spatial coherences formed by a -element interferometer array. Its invariance to phase corruption attributable to individual array elements acquired during the propagation and the measurement processes, subsequent calibration, and errors therein, makes it a valuable tool in interferometry applications that otherwise require high-accuracy phase calibration. However, its understanding has remained mainly mathematical and limited to the aperture plane (Fourier dual of the image plane). Here, we present a geometrical, image domain view of closure phase, which until now has been lacking. Using the principal triangle in a 3-element interference image formed by a triad of interferometer elements, we show that the properties of closure phase, particularly its invariance to multiplicative element-based corruption factors (even of a large magnitude) and to translation, are intricately related to the conserved properties of the triangle, namely, its shape, orientation, and size, which is referred herein as the ‘shape-orientation-size (SOS) conservation principle’. In the absence of a need for element-based amplitude calibration of the interferometer array (as is typical in optical interferometry), the principal triangle in any 3-element interference image formed from phase-uncalibrated spatial coherences is still a true and uncorrupted representation of the source object’s morphology, except for a possible shift. Based on this knowledge of the triangle SOS conservation principle, we present two geometric methods to measure the closure phase directly from a simple 3-element interference image (without requiring an aperture-plane view): (i) the closure phase is directly measurable from any one of the triangle’s heights, and (ii) the squared closure phase is proportional to the product of the areas enclosed by the triad of array elements and the principal triangle in the aperture and image planes, respectively. We validate the geometric understanding of closure phase in the image plane using observations with the Karl G. Jansky Very Large Array, and the Event Horizon Telescope. These results verify the SOS conservation principle across a wide range of radio interferometric conditions. This geometric insight can be potentially valuable to other interferometric applications, such as optical interferometry. We also generalise these geometric relationships to an N-element interferometer.
      PubDate: 2022-04-07
      DOI: 10.1017/pasa.2022.6
       
  • What is the SKA-Low sensitivity for your favourite radio source'

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      Authors: Sokolowski; M., Tingay, S. J., Davidson, D. B., Wayth, R. B., Ung, D., Broderick, J., Juswardy, B., Kovaleva, M., Macario, G., Pupillo, G., Sutinjo, A.
      First page: 15
      Abstract: The Square Kilometre Array (SKA) will be the largest radio astronomy observatory ever built, providing unprecedented sensitivity over a very broad frequency band from 50 MHz to 15.3 GHz. The SKA’s low frequency component (SKA-Low), which will observe in the 50–350 MHz band, will be built at the Murchison Radio-astronomy Observatory (MRO) in Western Australia. It will consist of 512 stations each composed of 256 dual-polarised antennas, and the sensitivity of an individual station is pivotal to the performance of the entire SKA-Low telescope. The answer to the question in the title is, it depends. The sensitivity of a low frequency array, such as an SKA-Low station, depends strongly on the pointing direction of the digitally formed station beam and the local sidereal time (LST), and is different for the two orthogonal polarisations of the antennas. The accurate prediction of the SKA-Low sensitivity in an arbitrary direction in the sky is crucial for future observation planning. Here, we present a sensitivity calculator for the SKA-Low radio telescope, using a database of pre-computed sensitivity values for two realisations of an SKA-Low station architecture. One realisation uses the log-periodic antennas selected for SKA-Low. The second uses a known benchmark, in the form of the bowtie dipoles of the Murchison Widefield Array. Prototype stations of both types were deployed at the MRO in 2019, and since then have been collecting commissioning and verification data. These data were used to measure the sensitivity of the stations at several frequencies and over at least 24 h intervals, and were compared to the predictions described in this paper. The sensitivity values stored in the SQLite database were pre-computed for the X, Y, and Stokes I polarisations in 10 MHz frequency steps, hour LST intervals, and resolution in pointing directions. The database allows users to quickly and easily estimate the sensitivity of SKA-Low for arbitrary observing parameters (your favourite object) using interactive web-based or command line interfaces. The sensitivity can be calculated using publicly available web interface (http://sensitivity.skalow.link) or a command line python package (https://github.com/marcinsokolowski/station_beam), which can also be used to calculate the sensitivity for arbitrary pointing directions, frequencies, and times without interpolations.
      PubDate: 2022-04-15
      DOI: 10.1017/pasa.2021.63
       
  • HST WFC3/Grism observations of the candidate ultra-high-redshift radio
           galaxy GLEAM J0917–0012

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      Authors: Seymour; N., Drouart, G., Noirot, G., Broderick, J. W., Turner, R. J., Shabala, S. S., Stern, D. K., Bellstedt, S., Driver, S., Davies, L., De Breuck, C. A., Afonso, J. A., Vernet, J. D. R., Galvin, T. J.
      First page: 16
      Abstract: We present Hubble Space Telescope Wide Field Camera 3 photometric and grism observations of the candidate ultra-high-redshift () radio galaxy, GLEAM J0917–0012. This radio source was selected due to the curvature in its 70–230 MHz, low-frequency Murchison Widefield Array radio spectrum and its faintness in K-band. Follow-up spectroscopic observations of this source with the Jansky Very Large Array and Atacama Large Millimetre Array were inconclusive as to its redshift. Our F105W and F0986M imaging observations detect the host of GLEAM J0917–0012 and a companion galaxy, one arcsec away. The G102 grism observations reveal a single weak line in each of the spectra of the host and the companion. To help identify these lines we utilised several photometric redshift techniques including template fitting to the grism spectra, fitting the ultraviolet (UV)-to-radio photometry with galaxy templates plus a synchrotron model, fitting of the UV-to-near-infrared photometry with EAZY, and fitting the radio data alone with RAiSERed. For the host of GLEAM J0917–0012 we find a line at m and the UV-to-radio spectral energy distribution (SED) fitting favours solutions at or . While this fitting shows a weak preference for the lower redshift solution, the models from the higher redshift solution are more consistent with the strength of the spectral line. The redshift constraint by RAiSERed of also supports the interpretation that this line could be Lyman at ; however EAZY favours the solution. We discuss the implications of both solutions. For the companion galaxy we find a line at m and the SED fitting favours solutions at...
      PubDate: 2022-04-12
      DOI: 10.1017/pasa.2022.4
       
  • Imaging the southern sky at 159 MHz using spherical harmonics with the
           engineering development array 2

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      Authors: Kriele; Michael A., Wayth, Randall B., Bentum, Mark J., Juswardy, Budi, Trott, Cathryn M.
      First page: 17
      Abstract: One of the major priorities of international radio astronomy is to study the early universe through the detection of the 21 cm HI line from the epoch of reionisation (EoR). Due to the weak nature of the 21 cm signal, an important part in the detection of the EoR is removing contaminating foregrounds from our observations as they are multiple orders of magnitude brighter. In order to achieve this, sky maps spanning a wide range of frequencies and angular scales are required for calibration and foreground subtraction. Complementing the existing low-frequency sky maps, we have constructed a Southern Sky map through spherical harmonic transit interferometry utilising the Engineering Development Array 2 (EDA2), a Square Kilometre Array (SKA) low-frequency array prototype system. We use the m-mode formalism to create an all-sky map at 159 MHz with an angular resolution of 3 degrees, with data from the EDA2 providing information over +60 degrees to –90 degrees in declination. We also introduce a new method for visualising and quantifying how the baseline distribution of an interferometer maps to the spherical harmonics and discuss how prior information can be used to constrain spherical harmonic components that the interferometer is not sensitive to.
      PubDate: 2022-04-22
      DOI: 10.1017/pasa.2022.2
       
  • System design and calibration of SITARA—a global 21 cm short spacing
           interferometer prototype

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      Authors: Thekkeppattu; Jishnu N., McKinley, Benjamin, Trott, Cathryn M., Jones, Jake, Ung, Daniel C. X.
      First page: 18
      Abstract: Global 21-cm experiments require exquisitely precise calibration of the measurement systems in order to separate the weak 21-cm signal from Galactic and extragalactic foregrounds as well as instrumental systematics. Hitherto, experiments aiming to make this measurement have concentrated on measuring this signal using the single element approach. However, an alternative approach based on interferometers with short baselines is expected to alleviate some of the difficulties associated with a single element approach such as precision modelling of the receiver noise spectrum. Short spacing Interferometer Telescope probing cosmic dAwn and epoch of ReionisAtion (SITARA) is a short spacing interferometer deployed at the Murchison Radio-astronomy Observatory (MRO). It is intended to be a prototype or a test-bed to gain a better understanding of interferometry at short baselines, and develop tools to perform observations and data calibration. In this paper, we provide a description of the SITARA system and its deployment at the MRO, and discuss strategies developed to calibrate SITARA. We touch upon certain systematics seen in SITARA data and their modelling. We find that SITARA has sensitivity to all sky signals as well as non-negligible noise coupling between the antennas. It is seen that the coupled receiver noise has a spectral shape that broadly matches the theoretical calculations reported in prior works. We also find that when appropriately modified antenna radiation patterns taking into account the effects of mutual coupling are used, the measured data are well modelled by the standard visibility equation.
      PubDate: 2022-04-21
      DOI: 10.1017/pasa.2022.13
       
  • The FAST Ultra-Deep Survey (FUDS): Observational strategy, calibration and
           data reduction

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      Authors: Xi; Hongwei, Peng, Bo, Staveley-Smith, Lister, For, Bi-Qing, Liu, Bin
      First page: 19
      Abstract: The FAST Ultra-Deep Survey (FUDS) is a blind survey that aims for the direct detection of H i in galaxies at redshifts . The survey uses the multibeam receiver on the Five-hundred-metre Aperture Spherical Telescope (FAST) to map six regions, each of size at high sensitivity () and high-frequency resolution (23 kHz). The survey will enable studies of the evolution of galaxies and their H i content with an eventual sample size of . We present the science goals, observing strategy, the effects of radio frequency interference at the FAST site, our mitigation strategies and the methods for calibration, data reduction and imaging as applied to initial data. The observations and reductions for the first field, FUDS0, are completed, with around 128 H i galaxies detected in a preliminary analysis. Example spectra are given in this paper, including a comparison with data from the overlapping GAL2577 field of Arecibo Ultra-Deep Survey.
      PubDate: 2022-04-26
      DOI: 10.1017/pasa.2022.16
       
  • MWA tied-array processing IV: A multi-pixel beamformer for pulsar surveys
           and ionospheric corrected localisation

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      Authors: Swainston; N. A., Bhat, N. D. R., Morrison, I. S., McSweeney, S. J., Ord, S. M., Tremblay, S. E., Sokolowski, M.
      First page: 20
      Abstract: The Murchison Widefield Array (MWA) is a low-frequency aperture array capable of high-time and frequency resolution astronomy applications such as pulsar studies. The large field-of-view of the MWA (hundreds of square degrees) can also be exploited to attain fast survey speeds for all-sky pulsar search applications, but to maximise sensitivity requires forming thousands of tied-array beams from each voltage-capture observation. The necessity of using calibration solutions that are separated from the target observation both temporally and spatially makes pulsar observations vulnerable to uncorrected, frequency-dependent positional offsets due to the ionosphere. These offsets may be large enough to move the source away from the centre of the tied-array beam, incurring sensitivity drops of in Phase II extended array configuration. We analyse these offsets in pulsar observations and develop a method for mitigating them, improving both the source position accuracy and the sensitivity. This analysis prompted the development of a multi-pixel beamforming functionality that can generate dozens of tied-array beams simultaneously, which runs a factor of ten times faster compared to the original single-pixel version. This enhancement makes it feasible to observe multiple pulsars within the vast field of view of the MWA and supports the ongoing large-scale pulsar survey efforts with the MWA. We explore the extent to which ionospheric offset correction will be necessary for the MWA Phase III and the low-frequency square kilometre array (SKA-low).
      PubDate: 2022-05-10
      DOI: 10.1017/pasa.2022.14
       
  • The relation between the radio emission of the core and host galaxy
           properties in Fanaroff–Riley type II radio galaxies

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      Authors: Mazoochi; F., Miraghaei, H., Riazi, N.
      First page: 21
      Abstract: We study the radio power of the core and its relation to the optical properties of the host galaxy in samples of high-excitation (HERG) and low-excitation (LERG) Fanaroff–Riley type II (FRII) radio galaxies. The radio galaxy sample is divided into two groups of core/non-core FRII, based on the existence of strong, weak or lack of single radio core component. We show that FRII LERGs with radio emission of the core have significantly higher [O III] line luminosities compared to the non-core LERG FRIIs. There is no significant difference between the hosts of the core and non-core FRIIs of LERG type in galaxy sizes, concentration indices, star formation rates, 4000-Å break strengths, colours, black hole masses, and black hole to stellar masses. We show that the results are not biased by the stellar masses, redshifts, and angular sizes of the radio galaxies. We argue that the detection of higher [O III] luminosities in the core FRIIs may indicate the presence of higher amounts of gas, very close to the active galactic nuclei (AGN) nucleus in the core FRIIs compared to the non-core FRIIs or may result from the interaction of the radio jets with this gas. The core and non-core FRIIs of the HERG type show no significant differences perhaps due to our small sample size. The effect of relativistic beaming on the radio luminosities and the contribution of restating AGN activity have also been considered.
      PubDate: 2022-05-10
      DOI: 10.1017/pasa.2022.15
       
  • A sensitive search for water masers associated with star formation regions
           in the Local Group Galaxy NGC 6822

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      Authors: Flanagan; C. J. P., Ellingsen, S. P., Cole, A. A.
      First page: 22
      Abstract: We report the results of a sensitive search for water maser emission in the Local Group Galaxy NGC 6822 with the Karl G. Jansky Very Large Array. The observations provide tentative single-epoch detections of four candidates, associated with two infrared-bright star formation regions (Hubble I/III and Hubble IV). The candidate maser detections are all offset from the velocity range where strong emission from Hi neutral gas is observed towards NGC 6822, with the closest offset by . Our observations include the location of NL1K, a previous tentative water maser detection in NGC 6822. We do not detect any emission from this location with a sensitivity limit approximately a factor of 5 better than the original Sardina Radio Telescope observations.
      PubDate: 2022-05-19
      DOI: 10.1017/pasa.2022.8
       
  • The fhd polarised imaging pipeline: A new approach to widefield
           interferometric polarimetry

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      Authors: Byrne; Ruby L., Morales, Miguel F., Hazelton, Bryna, Sullivan, Ian, Barry, Nichole
      First page: 23
      Abstract: We describe a new polarised imaging pipeline implemented in the fhd software package. The pipeline is based on the optimal mapmaking imaging approach and performs horizon-to-horizon image reconstruction in all polarisation modes. We discuss the formalism behind the pipeline’s polarised analysis, describing equivalent representations of the polarised beam response, or Jones matrix. We show that, for arrays where antennas have uniform polarisation alignments, defining a non-orthogonal instrumental polarisation basis enables accurate and efficient image reconstruction. Finally, we present a new calibration approach that leverages widefield effects to perform fully polarised calibration. This analysis pipeline underlies the analysis of Murchison Widefield Array data in Byrne et al. (2022, MNRAS, 510, 2011).
      PubDate: 2022-05-13
      DOI: 10.1017/pasa.2022.21
       
 
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