Evidence of unrelaxed IGM around IC 1262

¹ INAF-Osservatorio Astronomico di Brera, via Brera 28, 20121 Milano, Italy e-mail: ginevra.trinchieri@brera.inaf.it
² Institut für Astronomie, Universität Wien Türkenschanzstrasse 7, 1180 Wien, Austria
³ Max-Planck-Institut für extraterrestrische Physik, Giessenbachstrasse, 85740 Garching, Germany
⁴ Department of Physics and Astronomy, University of Alabama, Tuscaloosa, AL 35487, USA

Received: 1 August 2006
Accepted: 16 November 2006

Abstract

Aims.A peculiar morphology of the hot gas was discovered at the center of IC 1262 with the ROSAT HRI. Sensitive Chandra and XMM-Newton data were requested to investigate the characteristics of this structure to understand its nature.

Methods.We have exploited the high resolution and sensitivity of Chandra's ACIS-S to investigate the peculiar morphology and spectral characteristics of hot gas in the group around IC 1262. XMM-Newton data are only partially usable due to very heavy high background contamination, but they are useful to confirm and strengthen the results from Chandra.

Results.The Chandra data show a quite dramatic view of the IC 1262 system: a sharp discontinuity east of the central galaxy, with steep drops and a relatively narrow feature over 100 kpc long, plus an arc/loop to the N, are all indicative of a turmoil in the high energy component. Their morphologies could suggest them to be tracers of shocked material caused either by peculiar motions in the system or by a recent merger process, but the spectral characteristics indicate that the structure is cooler than its surroundings. The lack of evidence of significant structures in the velocity distribution of the group members and the estimated scale of the phenomenon make the interpretation of its physical nature challenging. We review a few possible interpretations, in light of similar phenomena observed in clusters and groups. The ram pressure stripping of a bright spiral galaxy, now near the center of the group, is a promising interpretation for most of the features observed. The relation with the radio activity requires a better sampling of the radio parameters that can only be achieved with deeper and higher resolution observations.