Speaker
Description
Our current knowledge of the properties of neutral gas at high redshifts has been obtained predominantly through absorption spectroscopy. The strongest HI absorbers, DLAs, are the most conspicuous, and make up the bulk of the cosmic HI budget. Their large HI column density and metal enrichment strongly implies -- although indirectly -- a close link with galaxies. Numerous studies have therefore attempted (with varying success) to connect the HI seen in absorption with emission lines from the associated galaxy.
In this talk, I will present observations from ALMA and other sub-mm/radio facilities that aim to measure the molecular and HI emission lines from galaxies associated with DLAs. ALMA has been transformative in this field by detecting -- with great efficiency -- the galaxy counterparts of DLAs. These observations show that the molecular mass of these HI absorption-selected galaxies is large, much larger than for other galaxy samples. The range of impact parameters between the molecular emission and the HI absorbers implies HI is extended far past the molecular emission of the galaxies. Finally, comparing the absorber kinematics with the kinematics of the molecular emission suggests a range of different physical origins of the HI detected in absorption, in some cases the gas seem to arise from an extended disk, whereas in other cases it arises from within the circumgalactic medium.
| Wish list question? | 3. At high redshift, how do HI emission-line and absorption-line observations relate to optical absorption-line and molecular emission-line measurements of cosmic gas reservoirs? |
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