CaII and DLA absorption line systems: dust, metals and star formation at 0.4<z<1.3

Abstract

Absorption line studies of galaxies along the line-of-sight to distant quasars allow a direct observational link between the properties of the extended gaseous disk/halo and of the star forming region of galaxies. In these proceedings we review recent work on CaII absorbers detected in the SDSS at 0.4<z<1.3 which, because of their dust content and chemical properties, may lie spatially closer to the central host galaxy than most DLAs. We present direct evidence for the presence of star formation, through observation of the [OII]3727,3730 emission line, in both CaII absorbers and MgII-selected Damped Lyman-alpha (DLA) systems. The measured star formation rate (SFR) from light falling within the SDSS fibre apertures (corresponding to physical radii of 6-9 h^{-1}kpc) is 0.11-0.48 Msol/yr for the CaII-absorbers and 0.11-0.14 Msol/yr for the MgII-selected DLAs. The contribution of both CaII absorbers and DLAs to the total observed SFR density, in the redshift range 0.4 < z < 1.3, is small, <10%. Our result contrasts with recent conclusions, based on the Schmidt law, that DLA absorbers can account for the majority of the total observed SFR density in the same redshift range.