HI Cosmology in the Local Universe with ALFALFA

Understand

The Arecibo Legacy Fast ALFA (ALFALFA) survey is an on-going second generation blind extragalactic HI survey exploiting Arecibo's superior sensitivity, angular resolution and digital technology to conduct a census of the local HI universe over a cosmologically significant volume.

• As of mid-2007, ~4500 good quality extragalactic HI line sources have been extracted in ~15% of the final survey area.
• ALFALFA is detecting HI masses as low as 10**6 Msun and as high as 10**10.8 Msun with positional accuracies typically better than 20 arcsec, allowing immediate identification of the most probable optical counterparts.
• Only 3% of all extragalactic HI sources and fewer than 1% of detections with M(HI) > 10**9.5 Msun cannot be identified with a stellar component.