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

Abstract

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' 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 ∼2 × 1036 erg s-1, much lower than previous studies of LMXBs in elliptical galaxies. The obtained XLF flattens significantly below Lx ∼ 5 × 1037 erg s -1 and follows the dN/dL K L∼-1 law in agreement with the behaviour found earlier for LMXBs in the Milky Way and in the bulge of M 31. © ESO 2006.