Astron. Astrophys. 326, 565-579 (1997)

A surprising correlation between X-ray and H morphologies
in early-type galaxies

G. Trinchieri1; ², L. Noris ³ and S. di Serego Alighieri <sup>4

1</sup> Osservatorio Astronomico di Brera, Via Brera 28, I-20121 Milano Italy
² Max Planck Institut für extraterrestrische Physik, Giessenbachstraße, D-85740 Garching, Germany
³ Università degli Studi di Milano, Via Celoria 16, I-20133 Milano, Italy
⁴ Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, I-50125 Firenze, Italy

Received 27 February 1997 / Accepted 23 May 1997

Abstract

High resolution X-ray images of three early type galaxies observed with the ROSAT HRI are presented. Data for NGC 1553 and NGC 5846 indicate that the emission is highly irregular, with interesting features on scales from a few arcsec to a few arcmin. The gas temperatures also vary both with the galactocentric radius and in correspondence to regions of higher emission and denser material.

Strikingly similar features are observed in the X-ray and H morphologies of NGC 1553 and NGC 5846, while smoother, more regular isophotes are observed in NGC 4649 at both wavelengths. A connection between these two kinds of emission therefore seems likely. In the light of our observations we discuss possible scenarios that can account for the connection between X-ray and H emissions.

Key words: X-rays: galaxiesgalaxies: elliptical and lenticulargalaxies: ISMgalaxies: individual: NGC 1553; NGC 4649; NGC 5846

Send offprint requests to: G. Trinchieri

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Contents

• 1. Introduction
• 2. Data analysis: HRI observations
  • 2.1. X-ray maps
  • 2.2. Azimuthal profiles
  • 2.3. Radial profiles
• 3. Spectral data from PSPC observations
• 4. Fluxes, luminosities and densities of the hot gas
• 5. Comparison between X-ray and H emissions
• 6. Discussion
• 7. Conclusions
• Acknowledgements
• References

© European Southern Observatory (ESO) 1997

Online publication: October 15, 1997
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