EDP Sciences
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Volume 447, Number 1, February III 2006
Page(s) 71 - 80
Section Extragalactic astronomy
DOI http://dx.doi.org/10.1051/0004-6361:20053420
A&A 447, 71-80 (2006)
DOI: 10.1051/0004-6361:20053420

The luminosity function of X-ray point sources in Centaurus A

R. Voss and M. Gilfanov

Max Planck Institut für Astrophysik, Germany
    e-mail: [voss;gilfanov]@mpa-garching.mpg.de

(Received 12 May 2005 / Accepted 15 September 2005)

We have studied the X-ray point source population of Centaurus A (NGC 5128) using data from four archival CHANDRA observations. We detected 272 point-like X-ray sources within a radius of 10$\arcmin$ from the centre. Approximately half of these are CXB sources, with the remaining half being LMXBs. The spatial distribution of the LMXBs, both azimuthally averaged and 2D, is consistent with the distribution of the K-band light observed in the 2MASS survey. After correction for the incompleteness effect we constrain the LMXB luminosity function down to ${\sim} 2\times 10^{36}$ erg s-1, much lower than previous studies of LMXBs in elliptical galaxies. The obtained XLF flattens significantly below $L_{\rm X}\sim 5\times
10^{37}$ erg s-1 and follows the ${\rm d}N/{\rm d}L\propto L^{-1}$ law in agreement with the behaviour found earlier for LMXBs in the Milky Way and in the bulge of M 31.

Key words: galaxies: individual: Centaurus A -- X-rays: binaries -- X-rays: galaxies

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