Understanding the relations between QSOs and their host galaxies from combined HST imaging and VLT spectroscopy

TL;DR

This study combines high-resolution HST imaging and VLT spectroscopy to analyze the impact of QSOs on their host galaxies, revealing that QSOs significantly influence gas ionization and dynamics over large scales, often linked to galactic interactions.

Contribution

It provides new insights into how QSOs interact with and affect their host galaxies, highlighting the role of galactic collisions in QSO activity and feedback.

Findings

QSOs significantly ionize their entire host galaxies.

Matter responsible for QSO light reflection moves away, likely accelerated by radiation pressure.

Large-scale phenomena like galactic collisions are linked to QSO triggering and influence.

Abstract

The host galaxies of six nearby QSOs are studied on the basis of high resolution HST optical images and spatially resolved VLT slit spectra. The gas ionization and velocity are mapped as a function of the distance to the central QSO. In the majority of the cases, the QSO significantly contributes to the gas ionization in its whole host galaxy, and sometimes even outside. Reflection or scattering of the QSO \ha line from remote regions of the galaxy is detected in several instances. The line shifts show that, in all cases, the matter responsible for the light reflection moves away from the QSO, likely accelerated by its radiation pressure. The two faintest QSOs reside in spirals, with some signs of a past gravitational perturbation. One of the intermediate luminosity QSOs resides in a massive elliptical containing gas ionized (and probably pushed away) by the QSO radiation. The other medium-power object is found in a spiral galaxy displaying complex velocity structure, with the central QSO moving with respect to the bulge, probably as a result of a galactic collision. The two most powerful objects are involved in violent gravitational interactions and one of them has no detected host. These results suggest that (1) large-scale phenomena, such as galactic collisions, are closely related to the triggering and the feeding of the QSO and (2) once ignited, the QSO has significant influence on its large-scale neighborhood (often the whole host and sometimes further away).