AAS 197, January 2001
Session 66. When the Universe was Mostly Gas
Oral, Tuesday, January 9, 2001, 1:30-3:00pm, Royal Palm 3/4

## [66.04] The Local Ly\alpha Forest: Relationship of Absorbers to Galaxies.

K. M. McLin, J. T. Stocke (CASA, University of Colorado), R. J. Weymann (Carnegie Observatories, Pasadena), S. V. Penton, J. M. Shull (CASA, University of Colorado)

We have conducted pointed galaxy redshift surveys in the directions of nearby AGN (typically closer than {\rm cz=30,000\,km\,s-1}) whose spectra contain local Ly\alpha forest absorption systems. The lowest column absorbers in our sample are comparable to lowest column systems found at high z, {\rm NHI ~ 10-12.5\,cm-2}, and are significantly lower in column than the HST Key Project'' absorbers measured with FOS. The sample of AGN used is from our HST study conducted with GHRS and STIS and has been reported elsewhere. Our goal is to understand the distribution of galaxies along these sightlines and to compare it with the distribution of the absorbers. This study involves ground based multiobject spectroscopy in the optical band undertaken at Las Campanas Observatory in Chile and at the WIYN telescope on Kitt Peak in Arizona. Our limiting magnitude in the optical is {\rm m = 19.0}, which corresponds to an absolute magnitude {\rm M = -16} at {\rm cz = 10,000\,km\,s-1} for {\rm \Omegao = 1} and {\rm Ho = 100\,km\,s-1}. For these same parameters the WIYN field of view covers an area of the sky 1.7 Mpc across; our Las Campanas fields are 560 kpc across. Our study includes several absorbers in galaxy voids'', as indicated by the CfA Redshift Survey. Though our data go much deeper than the CfARS over our small pencil beams, the void absorbers remain isolated and thus appear to be truly intergalactic, rather than part of galaxies or their halos. We find only one galaxy, with an impact parameter {\rm \lesssim 100\,kpc}, for which an absorber could plausibly be part of the galaxy's halo. This object is in the line of sight to 3C273, which passes through Virgo.