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We present measurements of the evolution of normal-galaxy X-ray emission from$z \approx$ 0-7 using local galaxies and galaxy samples in the 6 Ms ChandraDeep Field-South (CDF-S) survey. The majority of the CDF-S galaxies areobserved at rest-frame energies above 2 keV, where the emission is expected tobe dominated by X-ray binary (XRB) populations; however, hot gas is expected toprovide small contributions to the observed- frame < 1 keV emission at $z < 1$.We show that a single scaling relation between X-ray luminosity ($L_{\rm X}$)and star-formation rate (SFR) is insufficient for characterizing the averageX-ray emission at all redshifts. We establish that scaling relations involvingnot only SFR, but also stellar mass ($M_\star$) and redshift, providesignificantly improved characterizations of the average X-ray emission fromnormal galaxy populations at $z \approx$ 0-7. We further provide the firstempirical constraints on the redshift evolution of X-ray emission from bothlow-mass XRB (LMXB) and high-mass XRB (HMXB) populations and their scalingswith $M_\star$ and SFR, respectively. We find $L_{\rm 2-10 keV}({\rmLMXB})/M_\star \propto (1 + z)^{2-3}$ and $L_{\rm 2-10 keV}({\rm HMXB})$/SFR$\propto (1 + z)$, and show that these relations are consistent with XRBpopulation-synthesis model predictions, which attribute the increase in LMXBand HMXB scaling relations with redshift as being due to declining host galaxystellar ages and metallicities, respectively. We discuss how emission from XRBscould provide an important source of heating to the intergalactic medium in theearly Universe, exceeding that of active galactic nuclei.

The Evolution of Normal Galaxy X-ray Emission Through Cosmic History: Constraints from the 6 Ms Chandra Deep Field-South