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We 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. [ABSTRACT FROM AUTHOR]

We 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. [ABSTRACT FROM AUTHOR]

The Tully–Fisher Relation (TFR) is a well-known empirical relationship between the luminosity of a spiral galaxy and its circular velocity, allowing us to estimate redshift independent distances. Here we use high signal-to-noise H  i 21-cm integrated spectra from the second pilot data release (PDR2, 180 deg2) of the Widefield ASKAP L -band Legacy All-sky Blind surveY (WALLABY). In order to prepare for the full WALLABY survey, we have investigated the TFR in phase 2 of the pilot survey with a further three fields. The data were obtained with wide-field Phased Array Feeds on the Australian Square Kilometre Array Pathfinder (ASKAP) and have an angular resolution of 30 arcsec and a velocity resolution of |$\sim$| 4 km s−1. Galaxy luminosities have been measured from the Wide-field Infrared Survey Explorer , and optical galaxy inclinations from the Dark Energy Camera Legacy Survey. We present TFRs for wavelengths from 0.8 to 3.4  μ m. We examine sources of galaxy inclination data and investigate magnitudes from the DECam Local Volume Exploration Survey and DENIS catalogues and the 4HS target catalogue based on the VISTA Hemisphere Survey. We consider the baryonic TFR. These are all of interest for TFR using the full WALLABY survey of 200 000 galaxies. We demonstrate that WALLABY TFR distances can take their place among state-of-the-art studies of the local velocity field. [ABSTRACT FROM AUTHOR]

We explore the properties of an 'almost' dark cloud of neutral hydrogen (H  i) using data from the Widefield ASKAP L-band Legacy All-sky Survey (WALLABY). Until recently, WALLABY J103508 − 283427 (also known as H1032 − 2819 or LEDA 2793457) was not known to have an optical counterpart, but we have identified an extremely faint optical counterpart in the Dark Energy Spectroscopic Instrument (DESI) Legacy Imaging Survey Data Release 10. We measured the mean g -band surface brightness to be 27.0 ± 0.3 mag arcsec−2. The WALLABY data revealed the cloud to be closely associated with the interacting group Klemola 13 (also known as HIPASS J1034 − 28 and the Tol 9 group), which itself is associated with the Hydra cluster. In addition to WALLABY J103508 − 283427/H1032 − 2819, Klemola 13 contains 10 known significant galaxies and almost half of the total H  i gas is beyond the optical limits of the galaxies. By combining the new WALLABY data with archival data from the Australia Telescope Compact Array, we investigate the H  i distribution and kinematics of the system. We discuss the relative role of tidal interactions and ram pressure stripping in the formation of the cloud and the evolution of the system. The ease of detection of this cloud and intragroup gas is due to the sensitivity, resolution, and wide field of view of WALLABY, and showcases the potential of the full WALLABY survey to detect many more examples. [ABSTRACT FROM AUTHOR]

We report on the discovery of two potential polar ring galaxies (PRGs) in the WALLABY Pilot Data Release 1 (PDR1). These untargeted detections, cross-matched to NGC 4632 and NGC 6156, are some of the first galaxies where the H  i observations show two distinct components. We used the iDaVIE virtual reality software to separate the anomalous gas from the galactic gas and found that the anomalous gas comprises ∼50 per cent of the total H  i content of both systems. We have generated plausible 3D kinematic models for each galaxy, assuming that the rings are circular and inclined at 90° to the galaxy bodies. These models show that the data are consistent with PRGs but do not definitively prove that the galaxies are PRGs. By projecting these models at different combinations of main disc inclinations, ring orientations, and angular resolutions in mock data cubes, we have further investigated the detectability of similar PRGs in WALLABY. Assuming that these galaxies are indeed PRGs, the detectability fraction, combined with the size distribution of WALLABY PDR1 galaxies, implies an incidence rate of ∼1–3 per cent. If this rate holds true, the WALLABY survey will detect hundreds of new polar ring galaxies. [ABSTRACT FROM AUTHOR]

The WALLABY pilot survey has been conducted using the Australian SKA Pathfinder (ASKAP). The integrated 21-cm H  i line spectra are formed in a very different manner compared to usual single-dish spectra Tully–Fisher measurements. It is thus extremely important to ensure that slight differences (e.g. biases due to missing flux) are quantified and understood in order to maximise the use of the large amount of data becoming available soon. This article is based on four fields for which the data are scientifically interesting by themselves. The pilot data discussed here consist of 614 galaxy spectra at a rest wavelength of 21 cm. Of these spectra, 472 are of high enough quality to be used to potentially derive distances using the Tully–Fisher relation. We further restrict the sample to the 251 galaxies whose inclination is sufficiently close to edge-on. For these, we derive Tully–Fisher distances using the deprojected WALLABY velocity widths combined with infrared (WISE W 1) magnitudes. The resulting Tully–Fisher distances for the Eridanus, Hydra, Norma, and NGC4636 clusters are 21.5, 53.5, 69.4, and 23.0 Mpc, respectively, with uncertainties of 5–10 per cent, which are better or equivalent to the ones obtained in studies using data obtained with giant single dish telescopes. The pilot survey data show the benefits of WALLABY over previous giant single-dish telescope surveys. WALLABY is expected to detect around half a million galaxies with a mean redshift of |$z = 0.05 (200\, \mathrm{Mpc})$|⁠. This study suggests that about 200 000 Tully–Fisher distances might result from the survey. [ABSTRACT FROM AUTHOR]

We present results from our analysis of the Hydra I cluster observed in neutral atomic hydrogen (H  i) as part of the Widefield ASKAP L-band Legacy All-sky Blind Survey (WALLABY). These WALLABY observations cover a 60-square-degree field of view with uniform sensitivity and a spatial resolution of 30 arcsec. We use these wide-field observations to investigate the effect of galaxy environment on H  i gas removal and star formation quenching by comparing the properties of cluster, infall, and field galaxies extending up to ∼5 R 200 from the cluster centre. We find a sharp decrease in the H  i -detected fraction of infalling galaxies at a projected distance of ∼1.5 R 200 from the cluster centre from |$\sim 85{{\ \rm per\ cent}}$| to |$\sim 35{{\ \rm per\ cent}}$|⁠. We see evidence for the environment removing gas from the outskirts of H  i -detected cluster and infall galaxies through the decrease in the H  i to r -band optical disc diameter ratio. These galaxies lie on the star-forming main sequence, indicating that gas removal is not yet affecting the inner star-forming discs and is limited to the galaxy outskirts. Although we do not detect galaxies undergoing galaxy-wide quenching, we do observe a reduction in recent star formation in the outer disc of cluster galaxies, which is likely due to the smaller gas reservoirs present beyond the optical radius in these galaxies. Stacking of H  i non-detections with H  i masses below |$M_{\rm {HI}}\lesssim 10^{8.4}\, \rm {M}_{\odot }$| will be required to probe the H  i of galaxies undergoing quenching at distances ≳60 Mpc with WALLABY. [ABSTRACT FROM AUTHOR]

We use high-resolution ASKAP observations of galaxies in the Eridanus supergroup to study their H  i , angular momentum, and star formation properties, as part of the WALLABY pre-pilot survey efforts. The Eridanus supergroup is composed of three sub-groups in the process of merging to form a cluster. The main focus of this study is the Eridanus (or NGC 1395) sub-group. The baryonic specific angular momentum – baryonic mass (j b− M b) relation for the Eridanus galaxies is observed to be an unbroken power law of the form |$j_{\mathrm{b}} \propto M_{\mathrm{b}}^{0.57 \pm 0.05}$|⁠ , with a scatter of ∼0.10 ± 0.01 dex, consistent with previous works. We examine the relation between the atomic gas fraction, f atm, and the integrated atomic disc stability parameter q (the f atm− q relation), and find that the Eridanus galaxies deviate significantly from the relation owing to environmental processes such as tidal interactions and ram pressure affecting their H  i gas. We find that a majority of the Eridanus galaxies are H  i deficient compared to normal star-forming galaxies in the field. We also find that the star formation among the Eridanus galaxies may be suppressed owing to their environment, thus hinting at significant levels of pre-processing within the Eridanus sub-group, even before the galaxies have entered a cluster-like environment. [ABSTRACT FROM AUTHOR]

We present the Australian Square Kilometre Array Pathfinder (ASKAP) WALLABY pre-pilot observations of two 'dark' H  i sources (with H  i masses of a few times 108  |$\rm {M}_\odot$| and no known stellar counterpart) that reside within 363 kpc of NGC 1395, the most massive early-type galaxy in the Eridanus group of galaxies. We investigate whether these 'dark' H  i sources have resulted from past tidal interactions or whether they are an extreme class of low surface brightness galaxies. Our results suggest that both scenarios are possible, and not mutually exclusive. The two 'dark' H  i sources are compact, reside in relative isolation, and are more than 159 kpc away from their nearest H  i -rich galaxy neighbour. Regardless of origin, the H  i sizes and masses of both 'dark' H  i sources are consistent with the H  i size–mass relationship that is found in nearby low-mass galaxies, supporting the possibility that these H  i sources are an extreme class of low surface brightness galaxies. We identified three analogues of candidate primordial 'dark' H  i galaxies within the TNG100 cosmological, hydrodynamic simulation. All three model analogues are dark matter dominated, have assembled most of their mass 12–13 Gyr ago, and have not experienced much evolution until cluster infall 1–2 Gyr ago. Our WALLABY pre-pilot science results suggest that the upcoming large-area H  i surveys will have a significant impact on our understanding of low surface brightness galaxies and the physical processes that shape them. [ABSTRACT FROM AUTHOR]

We present observations of the Eridanus supergroup obtained with the Australian Square Kilometre Array Pathfinder (ASKAP) as part of the pre-pilot survey for the Widefield ASKAP L-band Legacy All-sky Blind surveY (WALLABY). The total number of detected H  i sources is 55, of which 12 are background galaxies not associated with the Eridanus supergroup. Two massive H  i clouds are identified and large H  i debris fields are seen in the NGC 1359 interacting galaxy pair, and the face-on spiral galaxy NGC 1385. We describe the data products from the source finding algorithm and present the basic parameters. The presence of distorted H  i morphology in all detected galaxies suggests ongoing tidal interactions within the subgroups. The Eridanus group has a large fraction of H  i -deficient galaxies as compared to previously studied galaxy groups. These H  i -deficient galaxies are not found at the centre of the group. We find that galaxies in the Eridanus supergroup do not follow the general trend of the atomic gas fraction versus stellar mass scaling relation, which indicates that the scaling relation changes with environmental density. In general, the majority of these galaxies are actively forming stars. [ABSTRACT FROM AUTHOR]

We present sofia  2, the fully automated 3D source finding pipeline for the WALLABY extragalactic H  i survey with the Australian SKA Pathfinder (ASKAP). sofia  2 is a reimplementation of parts of the original sofia pipeline in the c programming language and makes use of OpenMP for multithreading of the most time-critical algorithms. In addition, we have developed a parallel framework called sofia -X that allows the processing of large data cubes to be split across multiple computing nodes. As a result of these efforts, sofia  2 is substantially faster and comes with a much reduced memory footprint compared to its predecessor, thus allowing the large WALLABY data volumes of hundreds of gigabytes of imaging data per epoch to be processed in real time. The source code has been made publicly available to the entire community under an open-source licence. Performance tests using mock galaxies injected into genuine ASKAP data suggest that in the absence of significant imaging artefacts sofia  2 is capable of achieving near-100 per cent completeness and reliability above an integrated signal-to-noise ratio (SNR) of about 5–6. We also demonstrate that sofia  2 generally recovers the location, integrated flux, and w 20 line width of galaxies with high accuracy. Other parameters, including the peak flux density and w 50 line width, are more strongly biased due to the influence of the noise on the measurement. In addition, very faint galaxies below an integrated SNR of about 10 may get broken up into multiple components, thus requiring a strategy to identify fragmented sources and ensure that they do not affect the integrity of any scientific analysis based on the sofia  2 output. [ABSTRACT FROM AUTHOR]

We present an H  i study of the galaxy group LGG 351 using Widefield ASKAP L -band Legacy All-sky Blind Survey (WALLABY) early science data observed with the Australian Square Kilometre Array Pathfinder (ASKAP). LGG 351 resides behind the M 83 group at a velocity range (cz) of ∼3500–4800 km s−1 within the rich Hydra-Centaurus overdensity region. We detect 40 sources with the discovery of a tidally interacting galaxy pair and two new H  i sources that are not presented in previous optical catalogues. 23 out of 40 sources have new redshifts derived from the new H  i data. This study is the largest WALLABY sub-sample to date and also allows us to further validate the performance of ASKAP and the data reduction pipeline askapsoft. Extended H  i emission is seen in six galaxies indicating interaction within the group, although no H  i debris is found. We also detect H  i in a known ultra-faint dwarf galaxy (dw 1328−29), which demonstrates that it is not a satellite of the M 83 group as previously thought. In conjunction with multiwavelength data, we find that our galaxies follow the atomic gas fraction and baryonic Tully–Fisher scaling relations derived from the GALEX Arecibo SDSS Survey. In addition, majority of our galaxies fall within the star formation main sequence indicating inefficiency of gas removal processes in this loose galaxy group. [ABSTRACT FROM AUTHOR]

We present a Wide-field ASKAP L-Band Legacy All-sky Blind surveY (WALLABY) study of the nearby (v sys  = 915 km s−1) spiral galaxy IC 5201 using the Australian Square Kilometre Array Pathfinder (ASKAP). IC 5201 is a blue, barred spiral galaxy that follows the known scaling relations between stellar mass, SFR, H  i mass, and diameter. We create a four-beam mosaicked H  i image cube from 175 h of observations made with a 12-antenna sub-array. The root mean square noise level of the cube is 1.7 mJy beam−1 per channel, equivalent to a column density of |$N_{\rm H\, \small {I}}$|  = 1.4 × 1020 cm−2 over 25 km s−1. We report nine extragalactic H  i detections – five new H  i detections including the first velocity measurements for two galaxies. These sources are IC 5201, three dwarf satellite galaxies, two galaxies, and a tidal feature belonging to the NGC 7232/3 triplet and two potential infalling galaxies to the triplet. There is evidence of a previous tidal interaction between IC 5201 and the irregular satellite AM 2220−460. A close fly-by is likely responsible for the asymmetric optical morphology of IC 5201 and warping its disc, resulting in the irregular morphology of AM 2220−460. We quantify the H  i kinematics of IC 5201, presenting its rotation curve as well as showing that the warp starts at 14 kpc along the major axis, increasing as a function of radius with a maximum difference in position angle of 20°. There is no evidence of stripped H  i , triggered or quenched star formation in the system as measured using DECam optical and GALEX UV photometry. [ABSTRACT FROM AUTHOR]

A hierarchical Bayesian model is applied to the Cosmicflows-3 catalogue of galaxy distances in order to derive the peculiar velocity field and distribution of matter within z  ∼ 0.054. The model assumes the ΛCDM model within the linear regime and includes the fit of the galaxy distances together with the underlying density field. By forward modelling the data, the method is able to mitigate biases inherent to peculiar velocity analyses, such as the Homogeneous Malmquist bias or the lognormal distribution of peculiar velocities. The statistical uncertainty on the recovered velocity field is about 150 km s−1 depending on the location, and we study systematics coming from the selection function and calibration of distance indicators. The resulting velocity field and related density fields recover the cosmography of the Local Universe which is presented in an unprecedented volume of our Universe 10 times larger than previously reached. This methodology opens the doors to reconstruction of initial conditions for larger and more accurate constrained cosmological simulations. This work is also preparatory to larger peculiar velocity data sets coming from Wallaby, TAIPAN, or LSST. [ABSTRACT FROM AUTHOR]

In the originally published version of this manuscript, an acknowledgement was omitted: 'LVM acknowledges financial support from the grant IAA4SKA (Ref. R18-RT-3082) from the Economic Transformation, Industry, Knowledge and Universities Council of the Regional Government of Andalusia and the European Regional Development Fund from the European Union'. This is a correction to: O. I. Wong, A. R. H. Stevens, B.-Q. For, T. Westmeier, M. Dixon, S.-H. [Extracted from the article]