The Australian Square Kilometre Array Pathfinder (ASKAP) will revolutionise our knowledge of gas-rich galaxies in the Universe. In this video, we focus on visualising the galaxy catalogues created for two proposed extragalactic ASKAP neutral hydrogen (HI) surveys, based on semi-analytic models applied to cosmological N-body simulations (Duffy, et al 2012 *).

These surveys will find 40 times more galaxies, across 1000s of times more of the Universe, than any HI survey before. This type of work demands cutting edge simulations to create the predictions as well as visualise them.

Two survey projects are revealed in the video -- the first, known as WALLABY, or the ASKAP HI All-Sky Survey, is a shallow all-sky survey that will probe the mass and dynamics of over 600,000 galaxies. The second survey project, DINGO (overlayed and revealed in the later portion of the video), is a much deeper smaller-area HI survey, aiming to trace the evolution of HI in potentially 100,000 galaxies across the last 4 billion years of cosmic time.

The frames in the video were created by an interactive motion-compensated, point-based rendering system developed at ICRAR, called Gaius, which has been designed specifically for large scale astronomy and astrophysical datasets. For this video, the spatial coordinates in the catalogue were converted from right-ascension (RA) and declination (DEC) to direction cosines across the sky, and redshift (z) was used to provide a distance from the point of observation.

In this case, the centre represents the location of the observer (the earth, or more specifically, the site of the ASKAP telescope at The Murchison Radio-Astronomy Observatory (MRO) in rural Western Australia. Each point corresponds to one galaxy in the catalogue -- HI mass has been used to weight the elliptical radius of each point, and the colour corresponds to the observed colour range for the type of galaxy, based on its predicted star formation rate. Every galaxy from the simulated catalogues is shown. Each frame from the interactive renderer was saved to disk at 2k resolution as 32-bit floating point OpenEXR files, before being encoded to ProRes using Apple's Compressor. Titles and editing were done in Apple's FinalCut Pro X.

Predictions for ASKAP Neutral Hydrogen Surveys (accepted to MNRAS)

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