James Allison (University of Sydney)

James Allison colloquium: The history of cold gas in the Universe using the SKA

Abstract

The Square Kilometre Array (SKA) and its pathfinder telescopes will provide a unique perspective on the cold gas that fuels star formation and black hole growth in galaxies throughout cosmic history. By detecting the HI  21-cm line in absorption towards distant radio-loud active galactic nuclei (AGN), we will use the SKA to construct a census of neutral gas in intervening galaxies out to look back times of 10 billion years and beyond. I will discuss a recent paper in which I proposed a method for measuring the fraction of cold-phase atomic hydrogen using a statistical approach based on the number of expected detections with the SKA and its pathfinders. I will also present recent science results with the Australian SKA Pathfinder (ASKAP), which have successfully demonstrated the feasibility of carrying out such a survey.