Detection of a hot intergalactic medium in the spiral-only compact group SCG0018-4854

¹ INAF – Osservatorio Astronomico di Brera, via Brera 28, 20121 Milano, Italy e-mail: [ ginevra.trinchieri;angela.iovino] @brera.inaf.it
² ESO – Alonso de Cordova 3107, Vitacura, Casilla 19001, Santiago 19, Chile
³ CSIRO/ATNF – Paul Wild Observatory, Narrabri NSW 2390, Australia
⁴ Astrophysics Group, School of Physical and Geographical Sciences, Keele University, Keele, Staffordshire ST5 5BG, UK
⁵ Departamento de Astronoma, Universidad de Guanajuato, 36000 Guanajuato, Guanajuato, Mexico
⁶ Laboratoire AIM, CEA/DSM – CNRS – Université Paris Diderot, DAPNIA/SAp, 91191 Gif-sur-Yvette, France

Received: 30 January 2008
Accepted: 17 March 2008

Abstract

Aims. Compact groups of galaxies are excellent laboratories for studying galaxy interactions and their effects on the evolution of galaxies. In particular, dynamically young systems, with a large fraction of interacting, late type galaxies, have so far escaped proper studies in the X-ray band and their hot intergalactic medium properties are virtually unknown. Motivated by this lack of knowledge, we present a detailed investigation here of the X-ray properties of such a dynamically young system.

Methods. We obtained XMM-Newton observations of one spiral-only system in the new southern compact group catalogue: SCG0018-4854. We present here the results of the data analysis and discuss them in comparison with the few other similar systems also studied in the X-ray band.

Results. The 4 members of SCG0018-4854 emit at a level comparable to what is expected based on their optical properties. We detect the low level diffuse emission between galaxies, which is most likely due to the presence of the intergalactic medium. Compared to other spiral–only groups, SCG0018-4854 could be the coolest system detected so far, although the measurements have large uncertainties. These results indicate that high quality deep X-ray observations are needed to allow a proper study of the properties of the potential well of dynamically young systems, before more general conclusions can be drawn on their average characteristics.