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7th of February 2018
ATNF Colloquium
The history of cold gas in the Universe using the SKA
by James Allison (University of Sydney)
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.
The Figure above shows the number density of intervening Damped Lyman-alpha Absorbers (DLAs; N_{HI} > 2 x 10^{20} cm^{-2}) as a function of redshift, from optical (z > 1.7), UV (z < 1.7) and 21-cm line emission (z << 0.1) surveys. Recent results from a targeted survey of 50 radio-loud quasars with ASKAP are also shown (Sadler et al. in prep.). Adapted from Rao et al. (2017).

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