Quasars probing intermediate redshift star-forming galaxies

TL;DR

This study identifies and analyzes 46 intermediate redshift star-forming galaxies associated with quasars, exploring their emission properties, metallicities, and absorption features to understand the QSO absorber-galaxy connection.

Contribution

First comprehensive sample of intermediate redshift star-forming galaxies linked to quasars, combining emission and absorption data to study galaxy properties and their relation to absorbers.

Findings

Detected strong MgII, MgI, and FeII absorption lines in quasar spectra at galaxy redshifts.

Measured star-formation rates ranging from 0.2 to 20 solar masses per year.

Found potential correlation between galaxy metallicity and MgII absorption strength.

Abstract

We present a sample of 46 [OIII]-emitting galaxies at z<0.8 detected in the fibre spectra of quasars from the SDSS-DR7 through an automatic search procedure. We also detect [OII] and Hb emission lines from most of these galaxies in the SDSS spectra. We study both the emission and absorption properties of a sub-sample of 17 galaxies in the redshift range z=0.4-0.7, where MgII lines are covered by the SDSS spectra. The measured lower-limits on the star-formation rates of these galaxies are in the range 0.2-20 M_sun/yr. The emission line luminosities and (O/H) metallicities from R23 measured in this sample are similar to what is found in normal galaxies at these redshifts. Thus, this constitutes a unique sample of intermediate redshift star-forming galaxies where we can study the QSO absorber - galaxy connection. Strong MgII (W>1A) as well as MgI absorption lines are detected in the QSO spectra at the redshift of most of these galaxies. Strong FeII (W>1A) absorption lines are also generally detected whenever the appropriate wavelength ranges are covered. This suggests that most of these systems could be bona-fide Damped Lyman-alpha systems. We investigate various possible relations between the MgII rest equivalent widths and the emission line properties. We find a possible (2 sigma) correlation between the emission-line metallicity of the galaxies and the MgII rest equivalent width of the absorbers [truncated].