ABSTRACT. We present an initial survey of Mg II absorption characteristics in the halos of a carefully constructed, volume-limited subsample of galaxies embedded in the spectroscopic part of the Sloan Digital Sky Survey (SDSS). We observed quasars near sightlines to 20 low-redshift (z ~ 0.1), luminous (M _r + 5log h ≤–20.5) galaxies in SDSS DR4 and DR6 with the LRIS-B spectrograph on the Keck I telescope. The primary systematic criteria for the targeted galaxies are a redshift z 0.1 and the presence of an appropriate bright background quasar within a projected 75 h ^–1 kpc of its center, although we preferentially sample galaxies with lower impact parameters and slightly more star formation within this range. Of the observed systems, six exhibit strong (W _eq(2796) ≥ 0.3 Å) Mg II absorption at the galaxy's redshift, six systems have upper limits which preclude strong Mg II absorption, while the remaining observations rule out very strong (W _eq(2796) ≥ 1-2 Å) absorption. The absorbers fall at higher impact parameters than many non-absorber sightlines, indicating a covering fraction f_c 0.4 for ≥0.3 Å absorbers at z ~ 0.1, even at impact parameters ≤35 h ^–1 kpc (f _c ~ 0.25). The data are consistent with a possible dependence of covering fraction and/or absorption halo size on the environment or star-forming properties of the central galaxy.

Key words: galaxies: evolution; galaxies: ISM; quasars: absorption lines

^* The data presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation.

Print publication: Issue 6 (2009 December)
Received 2009 May 7, accepted for publication 2009 September 26
Published 2009 November 3