Beyond the Monsters: A More Complete Census of Black Hole Activity at Cosmic Dawn
/ Authors
Madisyn Brooks, J. Trump, R. Simons, Justin W. Cole, A. J. Taylor, M. Bagley, S. Finkelstein, Kelcey Davis, R. O. Amor'in, B. Backhaus
and 12 more authors
N. Cleri, M. Giavalisco, N. Grogin, M. Hirschmann, B. Holwerda, M. Huertas-Company, J. Kartaltepe, Dale D. Kocevksi, A. Koekemoer, R. Lucas, F. Pacucci, Xin Wang
/ Abstract
JWST has revealed an abundance of low-luminosity active galactic nuclei (AGN) at high redshifts ($z>3$), pushing the limits of black hole (BH) science in the early Universe. Results have claimed that these BHs are significantly more massive than expected from the BH mass-host galaxy stellar mass relation derived from the local Universe. We present a comprehensive census of the BH populations in the early Universe through a detailed stacking analysis of galaxy populations, binned by luminosity and redshift, using JWST spectroscopy from the CEERS, JADES, RUBIES, and GLASS extragalactic deep field surveys. Broad H$\alpha$ detections in $31\%$ of the stacked spectra (5/16 bins) imply median BH masses of $10^{5.21} - 10^{6.13}~ \rm{M_{\odot}}$ and the stacked SEDs of these bins indicate median stellar masses of $10^{7.84} - 10^{8.56} ~\rm{M_{\odot}}$. This suggests that the median galaxy hosts a BH that is at most a factor of 10 times over-massive compared to its host galaxy and lies closer to the locally derived $M_{BH}-M_*$ relation. We investigate the seeding properties of the inferred BHs and find that they can be well-explained by a light stellar remnant seed undergoing moderate Eddington accretion. Our results indicate that individual detections of AGN are more likely to sample the upper envelope of the $M_{BH}-M_*$ distribution, while stacking on ``normal"galaxies and searching for AGN signatures can overcome the selection bias of individual detections.