Low-redshift quasars in the SDSS Stripe 82 -- III MOS observations

TL;DR

This study investigates the environments of low-redshift quasars in SDSS Stripe 82, finding similar companion galaxy incidence to inactive galaxies but more frequent emission lines, indicating a possible link to recent star formation.

Contribution

It provides new spectroscopic data on quasar environments and compares companion galaxy properties with inactive galaxies, highlighting differences in emission line activity.

Findings

Approximately 50% of quasars have associated companion galaxies.

Companion galaxy incidence around quasars is similar to inactive galaxies.

Quasar companions show more emission lines, suggesting recent star formation.

Abstract

We present multi object optical spectroscopy of the galaxies in the environment of 12 low-redshift (z < 0.5) quasars and of 11 inactive massive galaxies chosen to match the properties of the quasar host galaxies to probe physical association and possible events of recent star formation. The quasars are selected from a sample of QSOs in the SDSS Stripe82 region for which both the host galaxy and the large scale environments were previously investigated. The new observations complement those reported in our previous works on close companion galaxies of nearby quasars. For the whole dataset we find that for about half (19 out of 44 ) of the observed QSOs there is at least one associated companion galaxy. In addition to the new spectroscopic observations, we add data from the SDSS database for the full sample of objects. We find that the incidence of companion galaxies in the fields of QSO (17%) is not significantly different from that of inactive galaxies (19%) similar to quasar hosts in redshift and mass. Nevertheless, the companions of quasars exhibit more frequently emission lines than those of inactive galaxies, suggesting a moderate link between the nuclear activity and recent star formation in their environments.