Volume 365, Number 1, January 2001
First Results from XMM-Newton
|Page(s)||L195 - L201|
|Published online||15 January 2001|
The central region of M 31 observed with XMM-Newton*
I. Group properties and diffuse emission
Department of Physics, University of California, Santa Barbara, Santa Barbara, CA 93106, USA
2 Mullard Space Science Laboratory, University College London, Holmbury St. Mary, Dorking RH5 6NT, UK
3 NIS-2, Space and Remote Sensing Sciences, Los Alamos National Laboratory, Los Alamos, NM 87545, USA
4 Department of Physics & Astronomy, University of Leicester, Leicester LE1 7RH, UK
5 SOC, VILSPA-ESA, Apartado 50727, 28080 Madrid, Spain
6 Istituto di Fisica Cosmica "G. Occhialini", Via Bassini 15, 20133 Milano, Italy
7 Columbia Astrophysics Laboratory, Columbia University, New York, NY 10027, USA
8 Max Planck Institut für Extraterrestrische Physik, Giessenbachstraße, 85741 Garching bei München, Germany
Corresponding author: R. E. Shirey, firstname.lastname@example.org
Accepted: 13 November 2000
We present the results of a study based on an XMM-Newton Performance Verification observation of the central 30´of the nearby spiral galaxy M 31. In the 34-ks European Photon Imaging Camera (EPIC) exposure, we detect 116 sources down to a limiting luminosity of #1 10#2 erg s-1 (0.3-12 keV, kpc). The luminosity distribution of the sources detected with XMM-Newton flattens at luminosities below ~2.5 1037 erg s-1 . We make use of hardness ratios for the detected sources in order to distinguish between classes of objects such as super-soft sources and intrinsically hard or highly absorbed sources. We demonstrate that the spectrum of the unresolved emission in the bulge of M 31 contains a soft excess which can be fitted with a ~0.35-keV optically-thin thermal-plasma component clearly distinct from the composite point-source spectrum. We suggest that this may represent diffuse gas in the centre of M 31, and we illustrate its extent in a wavelet-deconvolved image.
Key words: galaxies: individual: M 31 / galaxies: spiral / galaxies: general / galaxies: ISM / X-rays: galaxies
© ESO, 2001
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