astrolunch: Nissim Kanekar

Tue, 22/09/2020 - 12:30 to 13:30

Title: Cold Gas at High Redshift
Abstract:  The primary process by which massive galaxies form, whether violent mergers or slow gas accretion, remains an open question in cosmology. An allied question is when the disk galaxies observed today were formed. Observations of high-redshift galaxies have been focussed on "emission-selected" systems, which tend to pick out the brighter galaxies and are biased towards systems undergoing mergers. "Absorption-selected" galaxies, selected by their gas absorption in QSO spectra, pick out normal galaxies at high redshifts. The nature of such galaxies, selected by their damped Lyman-alpha absorption, has been an open question in the field of galaxy evolution for more than three decades. The critical problem in the field has been simply identifying the DLA host galaxies, before characterizing them, due to the difficulty of detecting a faint galaxy in the presence of
a bright background QSO. This talk will describe new results from Atacama Large
Millimeter/sub-millimeter Array studies of the host galaxies of DLAs at high redshifts z~2-4, using carbon monoxide and ionized carbon (CII-158 micron) emission to trace the nature of the galaxies. These have provided a new window on the nature of normal galaxies at high redshifts.