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This is an Open Access article, distributed under the terms of the Creative Commons Attribution licence (https://creativecommons.org/licenses/by/4.0/), which permits unrestricted re-use, distribution, and reproduction in any medium, provided the original work is properly cited.--Full list of 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.; Denes, H.; Di Teodoro, E. M.; For, B-Q; Foster, Tyler J.; Gomez, J. F.; Imai, H.; Joncas, G.; Kim, C-G; Lee, M-Y; Lynn, C.; Leahy, D.; Ma, Y. K.; Marchal, A.; McConnell, D.; Miville-Deschenes, M-A; Moss, V. A.; Murray, C. E.; Nidever, D.; Peek, J.; Staveley-Smith, L.; Tepper-Garcia, T.; Tremblay, C. D.; Uscanga, L.; van Loon, J. Th; Vazquez-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.; Stanimirovic, S., We present the most sensitive and detailed view of the neutral hydrogen ( HI ) 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 HI 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 ( 1.6mJy beam−1 ) per 0.98km s−1 spectral channel with an angular resolution of 30′′ ( ∼10pc ). 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 ∼25deg2 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 HI test observations. c The Author(s), 2022. Published by Cambridge University Press on behalf of the Astronomical Society of Australia., The Australian SKA Pathfinder is part of the Australia Telescope National Facility which is managed by CSIRO. Operation of ASKAP is funded by the Australian Government with support from the National Collaborative Research Infrastructure Strategy. ASKAP uses the resources of the Pawsey Supercomputing Centre. Establishment of ASKAP, the Murchison Radio-astronomy Observatory and the Pawsey Supercomputing Centre are initiatives of the Australian Government, with support from the Government of Western Australia and the Science and Industry Endowment Fund. We acknowledge the Wajarri Yamatji people as the traditional owners of the Observatory site. Pipeline development was tested on the OzSTAR supercomputer under the project code, oz145, which is available through Swinburne University’s Centre of Astrophysics and Supercomputing. This research was supported by the Australian Research Council (ARC) through grant DP190101571. N.M.-G. acknowledges the support of the ARC through Future Fellowship FT150100024. G. A. and J. F. G. acknowledge support from the State Agency for Research (10.13039/501100011033) of the Spanish MCIU, through grants AYA2017-84390-C2-1-R and PID2020-114461GB-I00 (co-funded by FEDER) and the ‘Center of Excellence Severo Ochoa’ award for the Instituto de Astrofsica de Andaluca (SEV-2017-0709). C. E. M. is supported by an NSF Astronomy and Astrophysics Postdoctoral Fellowship under award AST-1801471.

The Rapid ASKAP Continuum Survey (RACS) is the first large sky survey using the Australian Square Kilometre Array Pathfinder (ASKAP), covering the sky south of +41$^\circ$ declination. With ASKAP's large, instantaneous field of view, $\sim 31$ deg$^2$, RACS observed the entire sky at a central frequency of 887.5 MHz using 903 individual pointings with 15 minute observations. This has resulted in the deepest radio survey of the full Southern sky to date at these frequencies. In this paper, we present the first Stokes I catalogue derived from the RACS survey. This catalogue was assembled from 799 tiles that could be convolved to a common resolution of 25$^{\prime\prime}$, covering a large contiguous region in the declination range $\delta=-$80$^\circ$ to +30$^\circ$. The catalogue provides an important tool for both the preparation of future ASKAP surveys and for scientific research. It consists of $\sim$2.1 million sources and excludes the $|b, Comment: Accepted for Publication in PASA; 29 pages, 20 figures, 6 tables

We present the results of three separate searches for HI 21-cm absorption in a total of twelve damped Lyman-alpha absorption systems (DLAs) and sub-DLAs over the redshift range z = 0.86-3.37. We find no absorption in the five systems for which we obtain reasonable sensitivities and add the results to those of other recent surveys in order to investigate factors which could have an effect on the detection rate: We provide evidence that the mix of spin temperature/covering factor ratios seen at low redshift may also exist at high redshift, with a correlation between the 21-cm line strength and the total neutral hydrogen column density, indicating a roughly constant spin temperature/covering factor ratio for all of the DLAs searched. Also, by considering the geometry of a flat expanding Universe together with the projected sizes of the background radio emission regions, we find, for the detections, that the 21-cm line strength is correlated with the size of the absorber. For the non-detections it is apparent that larger absorbers (covering factors) are required in order to exhibit 21-cm absorption, particularly if these DLAs do not arise in spiral galaxies. We also suggest that the recent z = 2.3 detection towards TXS 0311+430 arises in a spiral galaxy, but on the basis of a large absorption cross-section and high metallicity, rather than a low spin temperature

Infrared-faint radio sources (IFRS) are a class of radio-loud (RL) active galactic nuclei (AGN) at high redshifts (z > 1.7) that are characterised by their relative infrared faintness, resulting in enormous radio-to-infrared flux density ratios of up to several thousand. We aim to test the hypothesis that IFRS are young AGN, particularly GHz peaked-spectrum (GPS) and compact steep-spectrum (CSS) sources that have a low frequency turnover. We use the rich radio data set available for the Australia Telescope Large Area Survey fields, covering the frequency range between 150 MHz and 34 GHz with up to 19 wavebands from different telescopes, and build radio spectral energy distributions (SEDs) for 34 IFRS. We then study the radio properties of this class of object with respect to turnover, spectral index, and behaviour towards higher frequencies. We also present the highest-frequency radio observations of an IFRS, observed with the Plateau de Bure Interferometer at 105 GHz, and model the multi-wavelength and radio-far-infrared SED of this source. We find IFRS usually follow single power laws down to observed frequencies of around 150 MHz. Mostly, the radio SEDs are steep, but we also find ultra-steep SEDs. In particular, IFRS show statistically significantly steeper radio SEDs than the broader RL AGN population. Our analysis reveals that the fractions of GPS and CSS sources in the population of IFRS are consistent with the fractions in the broader RL AGN population. We find that at least 18% of IFRS contain young AGN, although the fraction might be significantly higher as suggested by the steep SEDs and the compact morphology of IFRS. The detailed multi-wavelength SED modelling of one IFRS shows that it is different from ordinary AGN, although it is consistent with a composite starburst-AGN model with a star formation rate of 170 solar masses per year., 25 pages, 7 figures, 5 tables, accepted for publication in A&A

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Cool neutral gas provides the raw material for all star formation in the Universe, and yet, from a survey of the hosts of high redshift radio galaxies and quasars, we find a complete dearth of atomic (HI 21-cm) and molecular (OH, CO, HCO+ & HCN) absorption at redshifts z > 3. Upon a thorough analysis of the optical photometry, we find that all of our targets have ionising ultra-violet continuum luminosities of logL > 23 W/Hz. We therefore attribute this deficit to the traditional optical selection of targets biasing surveys towards the most ultra-violet luminous objects, where the intense radiation excites the neutral gas to the point where it cannot engage in star formation. However, this hypothesis does not explain why there is a critical luminosity, rather than a continuum where the detections gradually become fewer and fewer as the harshness of the radiation increases. We show that by placing a quasar within a galaxy of gas there is always a finite ultra-violet luminosity above which all of the gas is ionised. This demonstrates that these galaxies are probably devoid of star-forming material rather than this being at abundances below the sensitivity limits of current radio telescopes., To appear in Molecular Gas, Dust and Star Formation in Galaxies. Proceedings IAU Symposium No. 292