WALLABY Pilot Survey: HI gas disc truncation and star formation of
  galaxies falling into the Hydra I cluster
  We present results from our analysis of the Hydra I cluster observed in
neutral atomic hydrogen (HI) 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 HI gas removal and star formation quenching
by comparing the properties of cluster, infall and field galaxies extending up
to $\sim5R_{200}$ from the cluster centre. We find a sharp decrease in the
HI-detected fraction of infalling galaxies at a projected distance of
$\sim1.5R_{200}$ from the cluster centre from $\sim0.85\%$ to $\sim0.35\%$. We
see evidence for the environment removing gas from the outskirts of HI-detected
cluster and infall galaxies through the decrease in the HI 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 HI non-detections with HI masses below
$M_{\rm{HI}}\lesssim10^{8.4}\,\rm{M}_{\odot}$ will be required to probe the HI
of galaxies undergoing quenching at distances $\gtrsim60$ Mpc with WALLABY.
