Title: X‐Ray Sources in the Star‐Forming Galaxies NGC 4194 and NGC 7541
Abstract: We examine the X-ray point-source population and 2-10 keV luminosity for two galaxies with high star formation rates (SFRs), NGC 4194 and NGC 7541. The X-ray point-source luminosity function (XLF) for these two galaxies is consistent with the XLF found by Grimm et al. for a sample of star-forming galaxies. Combining our results with a sample of galaxies with SFRs above 1 M☉ yr−1, we find that the number of X-ray point sources above a luminosity of 2 × 1038 ergs s−1 is N = (1.8 ± 0.4) SFR/(M☉ yr −1) . This number is lower than previously inferred by Grimm et al. based on a sample of galaxies with lower SFRs. We find that the ratio of X-ray luminosity in the 2-10 keV band to SFR is LX/(1040 ergs s−1) = (0.37 ± 0.08) SFR/(M☉ yr−1). This value may serve as a calibration in attempts to use X-ray luminosity to measure the SFR of galaxies at cosmological distances. The ratio of mass accreted onto compact objects versus mass used to form stars is near 10–6. This ratio may be useful in constraining population synthesis models of X-ray binary formation in actively star-forming systems.