Abstract
We use high-quality, medium-resolution HST/COS observations of 75 UV-bright
AGN at redshifts $z_AGN< 0.85$ to construct the largest survey of the
low-redshift IGM to date. The catalog is comprised of 4369 individual
extragalactic absorption lines of HI and 20 different metal ions grouped
together into 2508 distinct redshift systems at $z_abs<0.75$ and
represents a significant improvement in total redshift pathlength and weak line
sensitivity over previous studies. The column-density distribution of HI
systems is seen to evolve both in amplitude and slope at $z< 0.47$. We observe
985 metal lines in 354 systems, and find that the fraction of absorbers
detected in metals is strongly dependent on HI column density. OVI absorbers
appear to evolve in the same sense as the Ly$\alpha$ forest. A velocity-space
two-point correlation function shows substantial clustering of HI absorbers on
scales of $\Delta v=50-300\rm~km~s^-1$ with no significant clustering at
larger $\Delta v$. Most of the clustering signal comes from the stronger
($N_HI>10^13.5~cm^-2$) absorbers particularly those with metal
absorption. The full catalog of absorption lines and fully-reduced spectra is
available via MAST as a high-level science product at
http://archive.stsci.edu/prepds/igm/.
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