Description
In this presentation, we detail a search conducted on WiggleZ galaxies cross-matched with bright ASKAP-FLASH sources for associated and intervening 21 cm absorption. HI has historically been difficult to probe at 0.4 < $z$ < 1.0 due to the faintness of the 21cm emission line. This is problematic due to the significant evolution of the Universe between the apparent peak of the cosmic star formation rate at $z$ ~ 2, and present day ($z$ = 0), where star formation rates have fallen by a factor of 10. We outline a pipeline to produce a catalogue of star-forming galaxies at these redshifts and demonstrate the similarity in characteristics with known star-forming galaxies in the WiggleZ survey. We present a new associated HI detection blueshifted by 160 km s$^{−1}$ from a galaxy at redshift $z$ = 0.864, and discuss the possibilities for stacking in 21cm absorption. We show that 21cm detection rates in star-forming galaxies and the general AGN population at these redshifts are not significantly different. The methodology of this work has now been demonstrated with ASKAP, but SKA offers the enhanced sensitivity and extended frequency range (HI to $z$ > 3) needed to make further progress.
