THE RELATIONSHIP BETWEEN INTERGALACTIC H I/O VI AND NEARBY (z < 0.017) GALAXIES

We analyze intergalactic H I and O VI absorbers with nu < 5000 km s(-1) in Hubble Space Telescope and Far Ultraviolet Spectroscopic Explorer spectra of 76 active galactic nuclei. The baryons traced by H I/O VI absorption are clearly associated with the extended surroundings of galaxies; for impact parameters < 400 kpc they are 2-4 times more numerous as those inside the galaxies. This large reservoir of matter likely plays a major role in galaxy evolution. We tabulate the fraction of absorbers having a galaxy of a given luminosity within a given impact parameter (rho) and velocity difference (Delta nu), as well as the fraction of galaxies with an absorber closer than a given rho and Delta nu. We identify possible "void absorbers" (rho > 3 Mpc to the nearest L(*) galaxy), although nu < 2500 km s(-1) all absorbers are within 1.5 Mpc of an L > 0.1 L(*) galaxy. The absorber properties depend on rho, but the relations are not simple correlations. For four absorbers with rho = 50-350 kpc from an edge-on galaxy with known orientation of its rotation, we find no clear relation between absorber velocities and the rotation curve of the underlying galaxy. For rho < 350 kpc, the covering factor of Ly alpha (O VI) around L > 0.1 L(*) galaxies is 100% (70%) for field galaxies and 65% ( 10%) for group galaxies; 50% of galaxy groups have associated Lya. All O VI absorbers occur within 550 kpc of an L > 0.25 L(*) galaxy. The properties of three of 14 O VI absorbers are consistent with photoionization, for five the evidence points to collisional ionization; the others are ambiguous. The fraction of broad Lya lines increases from z = 3 to z = 0 and with decreasing impact parameter, consistent with the idea that gas inside similar to 500 kpc from galaxies is heating up, although alternative explanations cannot be clearly excluded.