From voids to clusters: HI imaging surveys of galaxies in different environments

Our understanding of the formation and evolution of galaxies and the large scale structure has advanced enormously over the last decade, thanks to an impressive synergy between theoretical and observational efforts. While the growth of the dark matter component seems well understood, the physics of the gas, during its accretion, removal and/or depletion is less well understood. Increasingly large scale optical surveys are tracing out the cosmic web of filaments and voids and mathematical tools have been developed to describe these structures and identify galaxies in specific environments. H~I imaging surveys begin to answer the question: how do galaxies get and lose their gas. The best evidence for ongoing gas accretion is found in the lowest density environments, while removal of gas in the highest density environments stops star formation and reddens the galaxies. Although current HI emission surveys are mostly limited to redshifts less than 0.2, several HI imaging telescopes are being commissioned or planned that will be able to observe out to larger redshifts. I will conclude with a brief discussion of what will soon be possible.

Cody Hall

Jacqueline van Gorkom (Columbia)

November 16, 2012
14:00 - 15:00