A Census of Photometrically Selected Little Red Dots at 4 < z < 9 in JWST Blank Fields

Abstract

Observations with the James Webb Space Telescope (JWST) have uncovered numerous faint active galactic nuclei (AGN) at $z\sim 5$ and beyond. These objects are key to our understanding of the formation of supermassive black holes (SMBHs), their co-evolution with host galaxies, as well as the role of AGN in cosmic reionization. Using photometric colors and size measurements, we perform a search for compact red objects in an array of blank deep JWST/NIRCam fields totaling $\sim 640$ arcmin${}^2$. Our careful selection yields 260 reddened AGN candidates at $4<z_{\mathrm{phot}}<9$, dominated by a point-source like central component ($⟨r_{\mathrm{eff}}⟩<130$ pc) and displaying a dichotomy in their rest-frame colors (blue UV and red optical slopes). Quasar model fitting reveals our objects to be moderately dust extincted ($A_{\mathrm{V}}\sim 1.6$), which is reflected in their inferred bolometric luminosities of $L_{\mathrm{bol}}$ = 10${}^{44-47}$ erg/s, and fainter UV magnitudes $M_{\mathrm{UV}}\simeq$ $-17$ to $-22$. Thanks to the large areas explored, we extend the existing dusty AGN luminosity functions to both fainter and brighter magnitudes, estimating their number densities to be $\times 100$ higher than for UV-selected quasars of similar magnitudes. At the same time they constitute only a small fraction of all UV-selected galaxies at similar redshifts, but this percentage rises to $\sim$10\% for $M_{UV}\sim -22$ at $z\sim 7$. Finally, assuming a conservative case of accretion at the Eddington rate, we place a lower limit on the SMBH mass function at $z\sim 5$, finding it to be consistent with both theory and previous JWST observations.

23 pages, 6 figures, 4 tables. ApJ Accepted. Full source table here: https://github.com/VasilyKokorev/lrd_phot