Using Blind HI Surveys to Study Galaxy Evolution Across Cosmic Time

Ximena Fernandez

Department of Astronomy, Columbia University

Neutral hydrogen (HI) is a key ingredient in galaxy assembly since it is the raw fuel for star formation. Until recently, most of the HI blind surveys have been done locally (z < 0.08) due to instrument limitations. This is dramatically changing with recent upgrades of existing radio telescopes and new facilities that will come online in the coming years, capable of simultaneously observing a wide redshift range. The Blind Ultradeep HI Survey (BUDHIES) is the first study to use this capability, observing two large volumes each centered around a cluster at z=0.2. I will briefly summarize key results from this survey and present on-going work that relates the gas content to the star formation rate for galaxies in and around the clusters. I will then talk about the COSMOS HI Large Extragalactic Survey (CHILES). This is the first HI survey that instantaneously covers the entire redshift range 0 < z < 0.5. Once completed, the 1000 hours will result in approximately 300 HI images of galaxies in different environments. I will describe the science goals of the survey, what we learned from a pilot study, and present preliminary results for the first 200 hours of observations.