- Broida 1640
Gwen Rudie, The Carnegie Observatories
The exchange of gas between galaxies and intergalactic space is a crucial but poorly-understood aspect of galaxy formation. The gas near galaxies is the reservoir for future accretion and the fuel for star formation. Galaxies also expel gas in large-scale winds, a process that is expected to regulate star formation and through it, the evolutionary paths of galaxies. Measurements of the distribution, kinematics, temperature, and chemical enrichment of this "circumgalactic" gas provide vital constraints on galaxy-scale outflows.
I will present results from the Keck Baryonic Structure Survey (KBSS), a unique spectroscopic survey designed to explore both the properties of distant galaxies and their connection with the surrounding intergalactic gas. The KBSS is optimized to trace the peak epoch of star formation in the Universe (z~2-3, lookback times of 10-11 Gyr). It combines large galaxy redshift surveys with spectroscopy of background quasars against which the foreground circumgalactic gas is seen in absorption. The KBSS is the largest survey of its kind, with 900 foreground galaxies. Combined with detailed analysis of the quasar spectra, this survey has provided an unprecedented view of the circumgalactic medium in the early Universe. My analysis provides evidence of gas inflow and outflow as well as accretion shocks or hot outflows from these forming galaxies. I will compare these observations with recent theoretical predictions, highlighting discrepancies that show our theoretical picture of gas flows into and out of galaxies is incomplete.