S. Mineo, M. Gilfanov, R. Sunyaev
We investigate the relation between total X-ray emission from star-forming galaxies and their star formation activity. Using nearby late-type galaxies and ULIRGs from Paper I and star-forming galaxies from Chandra Deep Fields, we construct a sample of 54 galaxies spanning the redshift range z\approx0-1.3 and the SFR range ~0.1-10^{3} Msun/yr. In agreement with previous results, we find that the Lx-SFR relation is consistent with a linear law both at z=0 and for the z=0.1-1.3 CDF galaxies, within the statistical accuracy of ~0.1 in the slope of the Lx-SFR relation. For the total sample, we find a linear scaling relation Lx/SFR\approx(3.5\pm0.4)\times10^{39}(erg/s)/(Msun/yr), with a scatter of \approx0.4 dex. About ~3/4 of the 0.5-8 keV luminosity generated per unit SFR is provided by HMXBs. We find no statistically significant trends in the Lx/SFR ratio with the redshift or star formation rate and constrain the amplitude of its variations by \lesssim0.1-0.2 dex. These properties make X-ray observations a powerful tool to measure the star formation rate in normal star-forming galaxies that dominate the source counts at faint fluxes.
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http://arxiv.org/abs/1207.2157
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