Deep near-infrared imaging of the HE0450-2958 system

TL;DR

Deep near-infrared imaging of the HE0450-2958 system reveals a potential off-center host galaxy near the quasar, suggesting a collision event, and clarifies the nature of the previously undetected host galaxy.

Contribution

This study provides the first near-IR detection of the host galaxy candidate near HE0450-2958 using deep VLT observations and advanced deconvolution techniques.

Findings

Detection of a bright, compact emission region near the QSO in near-IR images.

Evidence suggesting the blob is a star-forming, off-center host galaxy.

Indications of a violent collision between the host galaxy and its companion.

Abstract

The QSO HE0450-2958 and the companion galaxy with which it is interacting, both ultra luminous in the infrared, have been the subject of much attention in recent years, as the quasar host galaxy remained undetected. This led to various interpretations on QSO and galaxy formation and co-evolution, such as black hole ejection, jet induced star formation, dust obscured galaxy, or normal host below the detection limit. We carried out deep observations in the near-IR in order to solve the puzzle concerning the existence of any host. The object was observed with the ESO VLT and HAWK-I in the near-IR J-band for 8 hours. The images have been processed with the MCS deconvolution method (Magain, Courbin & Sohy, 1998), permitting accurate subtraction of the QSO light from the observations. The compact emission region situated close to the QSO, called the blob, which previously showed only gas emission lines in the optical spectra, is now detected in our near-IR images. Its high brightness implies that stars likely contribute to the near-IR emission. The blob might thus be interpreted as an off-centre, bright and very compact host galaxy, involved in a violent collision with its companion.