Deep near-infrared imaging of the HE0450-2958 system

Institut d'Astrophysique et de Géophysique, Université de Liège, allée du 6 août 17, 4000 Liège, Belgium e-mail: gletawe@ulg.ac.be

Received: 1 February 2010
Accepted: 18 March 2010

Abstract

Context. 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.

Aims. We carried out deep observations in the near-IR in order to solve the puzzle concerning the existence of any host.

Methods. The object was observed with the ESO VLT and HAWK-I in the near-IR J-band for 8 h. The images have been processed with the MCS deconvolution method, permitting accurate subtraction of the QSO light from the observations.

Results. 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.