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S. V. Penton, J. T. Stocke (Center for Astrophysics and Space Astronomy (CASA) & University of Colorado - Boulder (CU)), J. M. Shull (CASA/CU & JILA (National Institute of Standards and Technology))
We combine the results of 15 low-z HST/STIS/G140M extragalactic sightlines with 15 GHRS/G160M sightlines to explore the very local (z < 0.07, cz \le 20,000~km s-1) Ly\alpha forest. Together, these 30 sightlines sample 346,000 km s-1 (z=1.15) of the local universe, of which about half represents pathlength through galaxy voids. We will explore the distribution of the detected Ly\alpha absorptions in these sightlines in terms of void vs statistics, the two-point correlation function along individual sightlines, and nearest galaxy neighbor statistics (based upon the September 2000 CfA redshift catalogue). We will also present the rest-frame equivalent width (\mathcal{W}) dependent absorber density, dN(\mathcal{W})/dz (the number of detected absorbers (N) per unit redshift for a given \mathcal{W}), and the column density spectrum, d2 N/dz dNHI (the column density distribution per unit redshift) of low-z Ly\alpha absorbers. The accounting of the varying spectral sensitivity as a function of wavelength of our observations allows us to explore the low-z Ly\alpha forest at \mathcal{W}s as low as 10 mÅ\ (\log NHI ~ 12.3).
This work is based on observations with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc. under NASA contract No. NAS5-26555. This research was supported by HST guest observer grant GO-06593.01-95A, and by the HST/COS project(NAS5-98043).