Speaker
Description
We present the results of a pilot study using the Australian SKA Pathfinder (ASKAP) radio telescope to search for 21cm neutral hydrogen (HI) absorption in distant galaxies that lie along the line of sight to bright background radio sources. This has allowed us to identify a small sample of galaxies in the redshift range $0.4 < z < 1$ selected on the basis of their HI content alone, without reference to any of their optical properties. We discuss the nature of these distant HI-selected galaxies, based on follow-up observations at other wavelengths, and show how our 21cm data can set constraints on the typical HI spin temperature and CNM fraction at cosmological distances. We also provide a first 21cm-based estimate of the DLA number density at redshift $z \sim 0.6$, and outline the prospects for the much larger ASKAP FLASH 21cm HI absorption survey to be carried out in the near future.
| Wish list question? | 1. Just how well do we know the cosmic evolution of Omega_HI(z) and Omega_H2(z)? |
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