James Webb Space Telescope Feed Post

UNCOVER: Candidate Red Active Galactic Nuclei at 3 < z < 7 with JWST and ALMA Published: 6/12/2023 9:00:01 PM Updated: 6/12/2023 9:00:01 PM

Paper abstract: The James Webb Space Telescope (JWST) is revolutionizing our knowledge ofz>5 galaxies and their actively accreting black holes. Using the JWST Cycle 1Treasury program Ultradeep NIRSpec and NIRCam ObserVations before the Epoch ofReionization (UNCOVER) in the lensing field Abell 2744, we report theidentification of a sample of little red dots at 3 < z_{\rm{phot}} < 7 thatlikely contain highly-reddened accreting supermassive black holes. Using aNIRCam-only selection to F444W<27.7 mag, we find 26 sources over the ~45arcmin^{2} field that are blue in F115W-F200W~0 (or \beta_{\rmUV}~-2.0 for f_{\lambda} \propto \lambda^\beta), red in F200W-F444W =1-4 (\beta_{\rm opt} ~ +2.0), and are dominated by a point-source likecentral component. Of the 20 sources with deep ALMA 1.2-mm coverage, none aredetected individually or in a stack. For the majority of the sample, SED fitsto the JWST+ALMA observations prefer models with hot dust rather than obscuredstar-formation to reproduce the red NIRCam colors and ALMA 1.2-mmnon-detections. While compact dusty star formation can not be ruled out, thecombination of extremely small sizes (\langle r_e \rangle~50 pc aftercorrection for magnification), red rest-frame optical slopes, and hot dust canby explained by reddened broad-line active galactic nuclei (AGNs). Our targetshave faint M_{\rm 1450} ~ -14\ \, {\rm to} -18 mag but inferredbolometric luminosities of L_{\rm bol} = 10^{43}-10^{46} erg/s, reflectingtheir obscured nature. If the candidates are confirmed as AGNs with upcomingUNCOVER spectroscopy, then we have found an abundant population of reddenedluminous AGN that are at least ten times more numerous than UV-luminous AGN atthe same intrinsic bolometric luminosity.