Environments of QSOs at Redshifts 0.9 to 1.3

TL;DR

This study investigates the environments of quasars at redshifts 0.9 to 1.3, revealing that QSOs reside in denser, more disturbed regions with asymmetrical host galaxies and fainter nearby companions, compared to field galaxies.

Contribution

It provides new deep imaging analysis of QSO environments at intermediate redshifts, highlighting differences in asymmetry and density compared to field galaxies.

Findings

QSOs are in denser environments than the field.

QSO hosts are more disturbed than other galaxies.

Companions within 15 arcsec are fainter than average field galaxies.

Abstract

We analyse new deep g and i-band imaging with the CFHT of 16 QSOs in the redshift range 0.9 to 1.3. The principal points of interest are the symmetry and signs of tidal effects in the QSO hosts and nearby (`companion') galaxies. The sample measures are compared with similar measures on randomly selected field galaxy samples. Asymmetry measures are made for all objects to g ~22, and magnitudes of all galaxies 2 magnitudes fainter. The QSOs are found in denser environments than the field, and are somewhat offset from the centroid of their surrounding galaxies. The QSO hosts appear more disturbed than other galaxies. While the QSO companions and field galaxies have the same average asymmetry, the distribution of asymmetry values is different. QSO companions within 15 arcsec are fainter than average field galaxies. We discuss scenarios that are consistent with these and other measured quantities.