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Arxiv: The Rise of Faint, Red AGN at z>4: A Sample of Little Red Dots in the JWST Extragalactic Legacy Fields Published: 4/4/2024 7:39:21 PM Updated: 4/19/2024 6:10:25 PM

Paper abstract: We present a sample of 341 "little red dots" (LRDs) spanning the redshiftrange z~2-11 using data from the CEERS, PRIMER, JADES, UNCOVER and NGDEEPsurveys. These sources are likely heavily-reddened AGN that trace apreviously-hidden phase of dust-obscured black hole growth in the earlyUniverse. Unlike past use of color indices to identify LRDs, we employcontinuum slope fitting using shifting bandpasses to sample the same rest-frameemission blueward and redward of the Balmer break. This approach allows us toidentify LRDs over a wider redshift range and is less susceptible tocontamination from galaxies with strong breaks that otherwise lack a rising redcontinuum. The redshift distribution of our sample increases at z<8 and thenundergoes a rapid decline at z~4.5, which may tie the emergence, andobscuration, of these sources to the inside-out growth that galaxies experienceduring this epoch. We find that LRDs are 2-3 dex more numerous than brightquasars at z~5-7, but their number density is only 0.6-1 dex higher thanX-ray and UV selected AGN at these redshifts. Within our sample, we haveidentified the first X-ray detected LRDs at z=3.1 and z=4.66. An X-rayspectral analysis confirms that these AGN are moderately obscured with\log\,(N_{\rm H}/{\rm cm}^{2}) of 23.3^{+0.4}_{-1.3} and22.72^{+0.13}_{-0.16}. Our analysis reveals that reddened AGN emissiondominates their rest-optical light, while the rest-UV originates from theirhost galaxies. We also present NIRSpec follow-up spectroscopy of 17 LRDs thatshow broad emission lines consistent with AGN activity. The confirmed AGNfraction of our sample is 71\% for sources with F444W<26.5. In addition, wefind three LRDs with narrow blue-shifted Balmer absorption features in theirspectra, suggesting an outflow of high-density, low ionization gas from nearthe central engine of these faint, red AGN.