2015ApJ...806..136C

Using data from the DEEP2 galaxy redshift survey and the All Wavelength Extended Groth Strip International Survey we obtain stacked X-ray maps of galaxies at as a function of stellar mass. We compute the total X-ray counts of these galaxies and show that in the soft band (0.5-2 kev) there exists a significant correlation between galaxy X-ray counts and stellar mass at these redshifts. The best-fit relation between X-ray counts and stellar mass can be characterized by a power law with a slope of 0.58±0.1. We do not find any correlation between stellar mass and X-ray luminosities in the hard (2-7 kev) and ultra-hard (4-7 kev) bands. The derived hardness ratios of our galaxies suggest that the X-ray emission is degenerate between two spectral models, namely point-like power-law emission and extended plasma emission in the interstellar medium. This is similar to what has been observed in low redshift galaxies. Using a simple spectral model where half of the emission comes from power-law sources and the other half from the extended hot halo we derive the X-ray luminosities of our galaxies. The soft X-ray luminosities of our galaxies lie in the range 10³⁹- erg/s. Dividing our galaxy sample by the criteria, we find no evidence that our results for X-ray scaling relations depend on optical color.