The host galaxies of strong CaII quasar absorption systems at z < 0.5

We present new imaging and spectroscopic observations of the fields of five quasars with very strong intervening CaII absorption systems at redshifts z_abs < 0.5 selected from the Sloan Digital Sky Survey. Recent studies of these very rare absorbers indicate that they may be related to damped Lyman α systems (DLAs). In all five cases, we identify a galaxy at the redshift of the CaII system with impact parameters up to ~24kpc. In four out of five cases the galaxies are luminous (L ~= L*), metal-rich (Z ~= Z_solar), massive (velocity dispersion σ ~= 100 km s^-1) spirals. Their star formation rates (SFRs), deduced from Hα emission, are high, in the range SFR = 0.3 -30 Msolar yr^-1. In our analysis, we paid particular attention to correcting the observed emission-line fluxes for stellar absorption and dust extinction. We show that these effects are important for a correct SFR estimate; the difficulties of incorporating such corrections in previous low-z studies of DLA-selected galaxies has probably led to an underestimate of the star formation activity in at least some DLA hosts. We discuss possible links between CaII-selected galaxies and DLAs and outline future observations which will help clarify the relationship between these different classes of quasar absorbers.