Exploring Gravitationally Lensed z ≳ 6 X-Ray Active Galactic Nuclei Behind the RELICS Clusters
| Authors | |
|---|---|
| Year of publication | 2022 |
| Type | Article in Periodical |
| Magazine / Source | Astrophysical Journal |
| MU Faculty or unit | |
| Citation | |
| Web | https://iopscience.iop.org/article/10.3847/1538-4357/ac4ae5 |
| Doi | http://dx.doi.org/10.3847/1538-4357/ac4ae5 |
| Keywords | High-redshift galaxies; Active galactic nuclei; X-ray active galactic nuclei; Galaxy clusters; Gravitational lensing |
| Description | Although observations of high-redshift quasars demonstrate that many supermassive black holes (BHs) reached large masses within one billion years after the Big Bang, the origin of the first BHs is still a mystery. A promising way to constrain the origin of the first BHs is to explore the average properties of z ? 6 BHs. However, typical BHs remain hidden from X-ray surveys, which is due to their relatively faint nature and the limited sensitivity of X-ray telescopes. Gravitational lensing provides an attractive way to study this unique galaxy population as it magnifies the faint light from these high-redshift galaxies. Here, we study the X-ray emission originating from 155 gravitationally lensed z ? 6 galaxies that were detected in the Reionization Lensing Cluster Survey. We utilize Chandra X-ray observations to search for active galactic nuclei (AGNs) in the individual galaxies and in the stacked galaxy samples. We did not identify an individual X-ray source that was undoubtedly associated with a high-redshift galaxy. We stack the signal from all galaxies and do not find a statistically significant detection. We split our sample based on stellar mass, star formation rate, and lensing magnification and stack these subsamples. We obtain a 2.2? detection for massive galaxies with an X-ray luminosity of (3.7 ± 1.6) × 1042 erg s-1, which corresponds to a (3.0 ± 1.3) × 105 M? 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 ? 6 either accrete at a few percent of their Eddington rate and/or are 1–2 orders of magnitude less massive than expected based on the stellar mass of their host galaxy. |
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