XMM-Newton first-light observations of the Hickson galaxy group 16

Research output: Contribution to journalArticle


  • MJL Turner
  • JN Reeves
  • M Arnaud
  • M Barbera
  • PJ Bennie
  • M Boer
  • U Briel

Colleges, School and Institutes


This paper presents the XMM-Newton first-light observations of the Hickson-16 compact group of galaxies. Groups are possibly the oldest large-scale structures in the Universe, pre-dating clusters of galaxies, and are highly evolved. This group of small galaxies, at a redshift of 0.0132 (or 80 Mpc) is exceptional in the having the highest concentration of starburst or AGN activity in the nearby Universe. So it is a veritable laboratory for the study of the relationship between galaxy interactions and nuclear activity. Previous optical emission line studies indicated a strong ionising continuum in the galaxies, but its origin, whether from starbursts, or AGN, was unclear. Combined imaging and spectroscopy with the EPIC X-ray CCDs unequivocally reveals a heavily obscured AGN and a separately identified thermal (starburst) plasma, in NGC 835, NGC 833, & NGC 839. NGC 838 shows only starburst thermal emission. Starbursts and AGN can evidently coexist in members of this highly evolved system of merged and merging galaxies, implying a high probability for the formation of AGN as well as starbursts in post-merger galaxies.


Original languageEnglish
Pages (from-to)L110-L115
JournalAstronomy and Astrophysics
Publication statusPublished - 1 Jan 2001


  • galaxies : starburst, X-rays : galaxies, galaxies : active