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Astron. Astrophys. 344, 755-766 (1999)

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X-ray study of the NGC 383 group of galaxies and the source 1E 0104+3153

Stefanie Komossa and Hans Böhringer

Max-Planck-Institut für Extraterrestrische Physik, Postfach 1603, D-85740 Garching, Germany

Received 19 October 1998 / Accepted 11 January 1999


We present results from an analysis of the X-ray properties of the NGC 383 galaxy group based on ROSAT PSPC and HRI data. X-ray emission can be traced out to [FORMULA] Mpc, the estimated virial radius of the system. We determine a total mass of [FORMULA] [FORMULA] for the group inside this radius with a gas mass fraction of 21%. The intragroup gas temperature of 1.5 keV is both consistent with the galaxy velocity dispersion and the X-ray luminosity - temperature relation of groups and clusters suggesting that the group is fairly relaxed. This is also indicated by the almost spherically symmetric appearance of the group's X-ray halo.

The X-ray properties of the radio galaxy NGC 383 (3C 31) which is located near the center of the group are discussed. Its spectrum is best described by a two-component model, consisting of emission from a low-temperature Raymond-Smith plasma, and a hard tail. The emission from NGC 383 is not resolved by the ROSAT HRI. The possible interaction of the radio jets of 3C 31 with the IGM is studied.

A spatial, spectral and temporal analysis of the Einstein source 1E0104+3153 located within the field of view is performed, one goal being the identification of the optical counterpart (with both, a high-redshift BAL quasar and a nearby elliptical galaxy, member of a small group, located within the Einstein X-ray error circle). We find evidence that the IGM of the small group contributes significantly to the X-ray emission of 1E0104, which can be described by a Raymond-Smith model of [FORMULA] 2 keV and a soft X-ray luminosity of [FORMULA] erg/s.

Key words: cosmology: dark matter – galaxies: clusters: individual: NGC 383 group – galaxies: individual: NGC 383 = 3C31, 1E0104+3153 – galaxies: elliptical and lenticular, cD – X-rays: galaxies

Send offprint requests to: St. Komossa (skomossa@xray.mpe.mpg.de)

© European Southern Observatory (ESO) 1999

Online publication: March 29, 1999