Joint Astrophysics Colloquium

ALFALFA: HI cosmology at z=0

Martha Haynes

Cornell University

The Arecibo Legacy Fast ALFA (ALFALFA) survey is an on-going blind HI survey designed to obtain a census of HI-bearing objects over a cosmologically significant volume of the local universe. To date, about 77% of the ALFALFA observations have been completed, and the current working catalog contains some 13000 high quality detections extracted from about 2000 square degrees of sky. ALFALFA is specifically designed to detect gas rich low mass halos nearby and to probe the HI mass functions in different environments, including voids, nearby groups such as Leo, and the Virgo cluster. Here I will present an overview of recent ALFALFA results, especially those related to the determination of the local HI mass function and the “void” and “missing satellite” problems.