EPOCHS VII: Discovery of high redshift ($6.5 < z < 12$) AGN candidates in JWST ERO and PEARLS data

TL;DR

This paper identifies nine high-redshift AGN candidates ($6.5<z<12$) in JWST data, suggesting that AGN may be common in the early universe and providing insights into their properties and potential black hole growth.

Contribution

It introduces a robust, multi-step selection method for high-redshift AGN candidates using JWST data, and constrains the AGN fraction at $z>6.5$.

Findings

Nine AGN candidates identified at $6.5<z<12$

Lower bound on AGN fraction is $5 \u00b1 1$",

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Abstract

We present an analysis of a sample of robust high redshift galaxies selected photometrically from the `blank' fields of the Prime Extragalactic Areas for Reionization Science (PEARLS) survey and Early Release Observations (ERO) data of the James Webb Space Telescope (JWST) with the aim of selecting candidate high redshift active galactic nuclei (AGN). Sources were identified from the parent sample using a threefold selection procedure, which includes spectral energy distribution (SED) fitting to identify sources that are best fitted by AGN SED templates, a further selection based on the relative performance of AGN and non-AGN models, and finally morphological fitting to identify compact sources of emission, resulting in a purity-oriented procedure. Using this procedure, we identify a sample of nine AGN candidates at $6.5 < z < 12$, from which we constrain their physical properties as well as measure a lower bound on the AGN fraction in this redshift range of $5 \pm 1$\%. As this is an extreme lower limit due to our focus on purity and our SEDs being calibrated for unobscured Type 1 AGN, this demonstrates that AGN are perhaps quite common at this early epoch. The rest-frame UV colors of our candidate objects suggest that these systems are potentially candidate obese black hole galaxies (OBG), or AGN with very little galaxy component. We also investigate emission from our sample sources from fields overlapping with Chandra and VLA surveys, allowing us to place X-ray and 3 GHz radio detection limits on our candidates. Of note is a $z = 11.9$ candidate source exhibiting an abrupt morphological shift in the reddest band as compared to the bluer bands, indicating a potential merger or an unusually strong outflow.