A COS Survey of the Low-Redshift Intergalactic Medium
American Astronomical Society, AAS Meeting #221, id.245.04
Published in Jan 2013
In three years of science operations onboard HST, the Cosmic OriginsSpectrograph has generated an archive of far-ultraviolet AGN spectra of unprecedented breadth, depth, and quality. COS was designed to be sensitive to many important diagnostic lines in the far-UV (1135-1800A) in the low-redshift, "local" universe: Lya (z〈0.47), Lyb (0.1〈z〈0.7), OVI (0.1〈z〈0.7), SiIII (z〈0.5), CIV (z〈0.17), NeVIII (0.45〈z〈1.3), etc. We report on our ongoing survey of extragalactic absorption systems toward ~200 low- to moderate-redshift (z〈1.5), UV-bright AGN. When complete mid-2013), the COS IGM absorber catalog will provide an unbiased, statistical sampling of local intergalactic absorption along ~200 extragalactic sight lines. This significant cornerstone of the scientific legacy of COS is at least an order-of-magnitude improvement over previous low-z IGM surveys in total observed pathlength and number of absorbers as well as substantial improvements in sensitivity and uniformity. Of particular interest is the sensitivity of COS to weak and broad absorption. We discuss the scope of and methodology behind the catalog, several initial discoveries, and the overall statistical findings of the survey. Finally, we discuss the new areas of cosmology enabled by this expanded study.
(c) 2013: American Astronomical Society