Mg II ABSORPTION CHARACTERISTICS OF A VOLUME-LIMITED SAMPLE OF GALAXIES ATz∼ 0.1

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.