Searching for Mergers in Early-Type QSO Host Galaxies and a Control Sample of Inactive Ellipticals

TL;DR

Deep HST imaging uncovers signs of recent mergers in QSO host ellipticals, contrasting with inactive ellipticals which show little to no such features, implying mergers may trigger QSO activity.

Contribution

This study provides high-resolution evidence of merger signatures in QSO hosts previously classified as undisturbed ellipticals, challenging earlier assumptions.

Findings

Most QSO host galaxies show signs of recent interactions.

Inactive ellipticals lack comparable fine structures.

Mergers may play a role in triggering QSO activity.

Abstract

We present very deep HST/ACS images of five QSO host galaxies, classified as undisturbed ellipticals in earlier studies. For four of the five objects, our images reveal strong signs of interaction such as tidal tails, shells, and other fine structure, suggesting that a large fraction of QSO host galaxies may have experienced a relatively recent merger event. Our preliminary results for a control sample of inactive elliptical galaxies do not reveal comparable fine structure.