Issue |
A&A
Volume 586, February 2016
|
|
---|---|---|
Article Number | A64 | |
Number of page(s) | 23 | |
Section | Extragalactic astronomy | |
DOI | https://doi.org/10.1051/0004-6361/201526233 | |
Published online | 26 January 2016 |
XMM-Newton study of the Draco dwarf spheroidal galaxy ⋆
1
Institut für Astronomie und Astrophysik, Kepler Center for Astro and
Particle Physics, Eberhard Karls Universität Tübingen,
Sand 1,
72076
Tübingen,
Germany
e-mail:
saeedi@astro.uni-tuebingen.de
2
ISDC Data Center for Astrophysics, Université de
Genève, 16 Chemin
d’Ecogia, 1290
Versoix,
Switzerland
Received: 31 March 2015
Accepted: 2 October 2015
Aims. We present the results of the analysis of five XMM-Newton observations of the Draco dwarf spheroidal galaxy (dSph). The aim of the work is the study of the X-ray population in the field of the Draco dSph.
Methods. We classified the sources on the basis of spectral analysis, hardness ratios, X-ray-to-optical flux ratio, X-ray variability, and cross-correlation with available catalogues in X-ray, optical, infrared, and radio wavelengths.
Results. We detected 70 X-ray sources in the field of the Draco dSph in the energy range of 0.2 − 12 keV and classified 18 AGNs, 9 galaxies and galaxy candidates, 6 sources as foreground stars, 4 low-mass X-ray binary candidates, 1 symbiotic star, and 2 binary system candidates. We also identified 9 sources as hard X-ray sources in the field of the galaxy. We derived the X-ray luminosity function of X-ray sources in the Draco dSph in the 2 − 10 keV and 0.5 − 2 keV energy bands. Using the X-ray luminosity function in the energy range of 0.5 − 2 keV, we estimate that ~10 X-ray sources are objects in the Draco dSph. We have also estimated the dark matter halo mass that would be needed to keep the low-mass X-ray binaries gravitationally bound to the galaxy.
Key words: galaxies: individual: Draco dwarf spheroidal galaxy / X-rays: galaxies / X-rays: binaries
© ESO, 2016
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