Chandra monitoring observations of the Antennae andf M82 star-forming galaxies: the X-ray source populations and the shape of their luminosity function

We present results on the discrete X-ray sources of the Antennae and M82 galaxies, based on monitoring observations performed with Chandra. In the case of the Antennae we detect between 37 and 49 sources in each observation. After combining all the observations we detect a total of 120 sources down to a detection limit of ∼2×10³⁷ erg/s (D=19 Mpc). In the case of M82 we detect a total of 25 discrete sources down to a detection limit of ∼2×10³⁷ erg/s. We discuss the spectral and temporal characteristics of the sources and their implications for the sources' nature. We find that the X-ray sources follow diverse spectral variability patterns suggesting that they belong to different populations or long term states. This diversity is also observed within the class of Ultra-luminous sources. The discrete sources are in their majority associated with young star clusters, indicating that they are High Mass X-ray binaries. Finally, we present the X-ray luminosity functions (XLF) of the discrete sources from the individual as well as the co-added observations and we discuss the effect of source variability on the shape of the luminosity function. By comparing the XLF of the Antennae with the XLFs of other galaxies we investigate the link between stellar populations and the shape of the XLF.