Thez = 0.0912 andz = 0.2212 Damped Lyα Galaxies along the Sight Line toward the Quasar OI 363

Abstract

New optical and infrared observations along the sight line toward the quasar OI 363 (0738+313) are presented and discussed. Excluding quasars selectively observed because they were known to be located behind gas-rich galaxies and systems which lack confirming UV spectroscopic observations of the actual Lyα line, this sight line presently contains the two lowest redshift classical damped Lyα (DLA) quasar absorption-line systems found in survey mode (i.e., with N ≥ 2 × 1020 atoms cm-2), one at zabs = 0.0912 and the other at zabs = 0.2212. Our new observations suggest identifications for the DLA galaxy counterparts of these absorption-line systems. The z = 0.09 DLA galaxy appears to be an extended low surface brightness galaxy which is easily visible only in infrared images and shows possible rich morphological structure. Assuming there is no contribution from the quasar host galaxy, we place an upper limit on the K-band luminosity of the z = 0.09 DLA galaxy of LK ≤ 0.13L (for a cosmology with H0 = 65 km s-1 Mpc-1, Ω = 1, and Λ = 0). More realistically, a subtraction of the quasar nuclear and host light yields LK ≈ 0.08L. The impact parameter between the galaxy and quasar sight line is very small, b < 3.6 kpc (< 2''), which makes measurements difficult. The z = 0.22 DLA galaxy is an early-type dwarf with a K-band luminosity of LK≈ 0.1L at impact parameter b = 20 kpc. Its colors are neutral and consistent with star formation models, suggesting its formation epoch was less than a few Gyr ago (i.e., zf ≈ 0.3-0.9). Thus, it is conceivable that its progenitor originated from the population of faint blue galaxies seen at moderate redshifts. In general, these results serve to support mounting evidence that DLA galaxies are drawn from a wide variety of gas-rich galaxy types.