Astron. Astrophys. 327, 81-89 (1997)

The rich cluster of galaxies ABCG 85

II. X-ray analysis using the ROSAT HRI ^*

G.B. Lima Neto ^{1, 2}, V. Pislar ¹, F. Durret ^{1, 3}, D. Gerbal ^{1, 3} and E. Slezak <sup>4

1</sup> Institut d'Astrophysique de Paris, CNRS, Université Pierre et Marie Curie, 98bis Bd Arago, F-75014 Paris, France
² Observatoire de Lyon, Av. Charles André, F-69561 St Genis Laval Cedex, France
³ DAEC, Observatoire de Paris, Université Paris VII, CNRS (UA 173), F-92195 Meudon Cedex, France
⁴ Observatoire de la Côte d'Azur, B.P. 229, F-06304 Nice Cedex 4, France

Received 7 May 1997 / Accepted 17 June 1997

Abstract

We present a new X-ray analysis mainly based on ROSAT HRI data. The HRI spatial resolution combined with an improved wavelet analysis method and with complementary radio and optical data provides new results compared to a previous paper based on ROSAT PSPC data (Pislar et al. 1997). We use also redshift data in order to identify galaxies dynamically belonging to the main body of the cluster and/or to superimposed substructures.

Various kinds of emission are superimposed on a mean thermal X-ray emission due to the intra-cluster gas:
- an X-ray flux excess in the centre at a scale of 15-25 kpc;
- a south blob, partially generated by individual galaxies (such as the second brightest galaxy); the mean velocity and velocity dispersion of the galaxies located in this region are the same as those of the cluster as a whole: it therefore does not seem to be a bound subgroup;
- West emission due to a foreground group with self-emission from a Seyfert galaxy located at the north-west;
- emission in the south-west due to inverse Compton emission associated to a very steep radio source (the remnant of an active galactic nucleus).

We have examined the possibility for the central peak to be an "unusual" galaxy, as assumed for the central galaxy of J2310-43 (Tananbaum et al. 1997). We conclude on the existence of a cooling flow region, in which the presence of at least three small features certainly related to cooler blobs is revealed by the wavelet analysis.

We have performed a pixel-to-pixel modelling of the double X-ray emission. The large scale emission component is comparable to those derived from by the PSPC data and the small scale one is interpreted as a cooling-flow. A multiphase gas model analysis leads to a mass deposit of 50-150  .

Key words: galaxies: clusters: general; clusters: individual: ABCG 85 cooling flows X-rays: galaxies

* Based on ROSAT Archive data

Send offprint requests to: G.B. Lima Neto, gastao@iap.fr

SIMBAD Objects

Contents

• 1. Introduction
• 2. The data
  • 2.1. X-rays
  • 2.2. Optical
  • 2.3. Radio
• 3. Image analysis
  • 3.1. Comparison of PSPC and HRI images
    • 3.1.1. Central emission
    • 3.1.2. The south blob
  • 3.2. Central features
  • 3.3. Radio and X-ray comparison
• 4. Spectral properties
• 5. Modelling
  • 5.1. Untangling the cD emission from that of the cluster
  • 5.2. Comparison of the central galaxies of ABCG 85 and cluster J2310-43
  • 5.3. Cooling flow
• 6. Discussion and conclusions
• Acknowledgements
• Appendix A
  • Appendix A: the wavelet image reconstruction
• References

© European Southern Observatory (ESO) 1997

Online publication: April 8, 1998
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