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

TL;DR

This study investigates the properties of galaxies associated with strong CaII absorption systems at z<0.5, revealing that they are often luminous, metal-rich spirals with high star formation rates, and explores their potential connection to DLA systems.

Contribution

The paper provides new imaging and spectroscopic data linking CaII absorbers to specific galaxy types and emphasizes the importance of correcting for stellar absorption and dust extinction in SFR estimates.

Findings

Galaxies associated with CaII absorbers are luminous, metal-rich spirals.

Star formation rates in these galaxies are higher than previously estimated.

Correcting for stellar absorption and dust extinction significantly affects SFR calculations.

Abstract

We present new imaging and spectroscopic observations of the fields of five QSOs with very strong intervening CaII absorption systems at redshifts z<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 alpha systems (DLAs). In all five cases we identify a galaxy at the redshift of the CaII system with impact parameters up to ~24 kpc. In four out of five cases the galaxies are luminous (L ~L*), metal-rich (Z ~Zsun), massive (velocity dispersion, sigma ~100 km/s) spirals. Their star formation rates, deduced from Halpha emission, are high, in the range SFR = 0.3 - 30 Msun/yr. 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; their neglect 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 QSO absorbers.