2004ApJ...600...52H

We present high-resolution (∼2") H I 21 cm and CO(1-0) observations of the quasar (QSO) galaxy pair 0248+430. The QSO Q0248+430 (z_em=1.313) has been found to show two metal absorption-line systems at redshifts z_a∼0.052, which are consistent with the redshift of a foreground luminous infrared galaxy 15" (∼11 h^–1 kpc) away. In our observations, the CO emission of this foreground galaxy, G0248+430, shows broad velocity distribution (∼173 km/s) but is spatially confined to a small unresolved region less than 1.5x1.5/h.kpc; the H₂mass based on the traditional conversion factor is ~10¹⁰ M_☉, which is approximately 30 times the H₂mass within a similar region of the Milky Way. On the other hand, no significant H I 21 cm emission is found in the foreground galaxy; the mass of the neutral atomic hydrogen is less than 6x10⁸M_☉. Toward the QSO we discover a new H I 21 cm absorber with {integral}τdv∼0.26 km/s at the redshift of one of the metal absorption components; however, we did not detect significant CO(1-0) absorption toward the QSO. The H I column density is large enough for the absorber to be classified as a damped Lyα system. We also derive the H I mass and spin temperature for this metal-line absorption system. We discuss the relation of this H I absorber and the depletion of the H I in the foreground galaxy. We find that this H I absorber has very high metal abundance and is intrinsically different from the normal damped Lyα absorption systems, although both have similar spin temperatures and hydrogen column densities.