X-ray Emission in Non-AGN Galaxies at z ~ 1
  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 0.7 < z < 1.0 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 10^39-8x10^40, ergs/s. Dividing our galaxy sample
by the criteria U-B > 1, we find no evidence that our results for X-ray scaling
relations depend on optical color.
