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Astron. Astrophys. 351, L19-L22 (1999)


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Letter to the Editor

The nature of the hard X-ray power-law tail in M 87

Matteo Guainazzi 1 and Silvano Molendi 2

1 Astrophysics Division, Space Science Department of ESA, ESTEC, Postbus 299, 2200 AG Noordwijk, The Netherlands
2 Istituto di Fisica Cosmica "G.Occhialini", Via Bassini 15, 20133 Milano, Italy

Received 6 September 1999 / Accepted 13 October 1999

Abstract

Spatially-resolved spectroscopy of the elliptical galaxy M 87 with the MECS instrument on board BeppoSAX demonstrates that the hard X-ray power-law tail, originally discovered by ASCA (Matsumoto et al. 1996; Allen et al. 1999), originates in the innermost 2´. Our results are consistent with it being produced in an Accretion Dominated Flow, although a substantial jet contribution cannot be ruled out. An origin from a Seyfert-like nucleus is disfavored by our data. As a by-product of this result, we present an analysis of the thermal emission coming from the center of the Virgo cluster, which exhibits a strong positive radial temperature gradient, along with a radial decrease of the iron abundance.

Key words: accretion, accretion disks – galaxies: nuclei – galaxies: individual: M 87 – galaxies: clusters: individual: Virgo – X-rays: galaxies

Send offprint requests to: M.Guainazzi

© European Southern Observatory (ESO) 1999

Online publication: November 3, 1999

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