Probing the Accretion of Gas onto Galaxies: Opportunities and Pitfalls

Claude-Andr̩ Faucher-Gigu̬re

January 27, 2011

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Abstract: Galaxies must continuously accrete gas from the intergalactic medium in order to sustain their observed star formation rates. How this accretion proceeds is a fundamental problem in galaxy formation, as it determines how rapidly galaxies can grow as a function of mass and redshift, as well as the efficiency of preventive feedback processes. While theoretical work predicts that galaxies acquire most of their baryons via the ‘cold mode’, observations have so far not found clear traces of the cold streams. I will discuss results from a research program aimed at robustly quantifying the observational signatures of the cold mode, both in emission and in absorption. In doing so, I will highlight some of the theoretical challenges involved, which can lead to incorrect predictions and jeopardize this unique opportunity to test a physical prediction of galaxy formation if not addressed properly.