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Although observations of high-redshift quasars demonstrate that manysupermassive black holes (BHs) reached large masses within one billion yearsafter the Big Bang, the origin of the first BHs is still a mystery. A promisingway to constrain the origin of the first BHs is to explore the averageproperties of $z\gtrsim6$ BHs. However, typical BHs remain hidden from X-raysurveys, which is due to their relatively faint nature and the limitedsensitivity of X-ray telescopes. Gravitational lensing provides an attractiveway to study this unique galaxy population as it magnifies the faint light fromthese high-redshift galaxies. Here, we study the X-ray emission originatingfrom 155 gravitationally-lensed $z\gtrsim6$ galaxies that were detected in theRELICS survey. We utilize Chandra X-ray observations to search for AGN in theindividual galaxies and in the stacked galaxy samples. We did not identify anindividual X-ray source that was undoubtedly associated with a high-redshiftgalaxy. We stack the signal from all galaxies and do not find a statisticallysignificant detection. We split our sample based on stellar mass,star-formation rate, and lensing magnification and stack these sub-samples. Weobtain a $2.2\sigma$ detection for massive galaxies with an X-ray luminosity of$(3.7\pm1.6)\times10^{42} \ \rm{erg \ s^{-1}}$, which corresponds to a$(3.0\pm1.3)\times10^5 \ \rm{M_{\odot}}$ BH accreting at its Eddington rate.Other stacks remain undetected and we place upper limits on the AGN emission.These limits imply that the bulk of BHs at $z\gtrsim6$ either accrete at a fewpercent of their Eddington rate and/or are $1-2$ orders of magnitude lessmassive than expected based on the stellar mass of their host galaxy.

Exploring Gravitationally-Lensed $z\gtrsim6$ X-ray AGN Behind the RELICS clusters