TY - JOUR
T1 - COSMOS-Web: The over-abundance and physical nature of "little red dots"--Implications for early galaxy and SMBH assembly
AU - Akins, Hollis B.
AU - Casey, Caitlin M.
AU - Lambrides, Erini
AU - Allen, Natalie
AU - Andika, Irham T.
AU - Brinch, Malte
AU - Champagne, Jaclyn B.
AU - Cooper, Olivia
AU - Ding, Xuheng
AU - Drakos, Nicole E.
AU - Faisst, Andreas
AU - Finkelstein, Steven L.
AU - Franco, Maximilien
AU - Fujimoto, Seiji
AU - Gentile, Fabrizio
AU - Gillman, Steven
AU - Gozaliasl, Ghassem
AU - Harish, Santosh
AU - Hayward, Christopher C.
AU - Hirschmann, Michaela
AU - Ilbert, Olivier
AU - Kartaltepe, Jeyhan S.
AU - Kocevski, Dale D.
AU - Koekemoer, Anton M.
AU - Kokorev, Vasily
AU - Liu, Daizhong
AU - Long, Arianna S.
AU - McCracken, Henry Joy
AU - McKinney, Jed
AU - Onoue, Masafusa
AU - Paquereau, Louise
AU - Renzini, Alvio
AU - Rhodes, Jason
AU - Robertson, Brant E.
AU - Shuntov, Marko
AU - Silverman, John D.
AU - Tanaka, Takumi S.
AU - Toft, Sune
AU - Trakhtenbrot, Benny
AU - Valentino, Francesco
AU - Zavala, Jorge
PY - 2024/6/1
Y1 - 2024/6/1
N2 - JWST has revealed a population of compact and extremely red galaxies at $z>4$, which likely host active galactic nuclei (AGN). We present a sample of 434 ``little red dots'' (LRDs), selected from the 0.54 deg$^2$ COSMOS-Web survey. We fit galaxy and AGN SED models to derive redshifts and physical properties; the sample spans $z\sim5$-$9$ after removing brown dwarf contaminants. We consider two extreme physical scenarios: either LRDs are all AGN, and their continuum emission is dominated by the accretion disk, or they are all compact star-forming galaxies, and their continuum is dominated by stars. If LRDs are AGN-dominated, our sample exhibits bolometric luminosities $\sim10^{45-47}$ erg\,s$^{-1}$, spanning the gap between JWST AGN in the literature and bright, rare quasars. We derive a bolometric luminosity function (LF) $\sim100$ times the (UV-selected) quasar LF, implying a non-evolving black hole accretion density of $\sim10^{-4}$ M$_\odot$ yr$^{-1}$ Mpc$^{-3}$ from $z\sim2$-$9$. By contrast, if LRDs are dominated by star formation, we derive stellar masses $\sim10^{8.5-10}\,M_\odot$. MIRI/F770W is key to deriving accurate stellar masses; without it, we derive a mass function inconsistent with $\Lambda$CDM. The median stellar mass profile is broadly consistent with the maximal stellar mass surface densities seen in the nearby universe, though the most massive $\sim50$\% of objects exceed this limit, requiring substantial AGN contribution to the continuum. Nevertheless, stacking all available X-ray, mid-IR, far-IR/sub-mm, and radio data yields non-detections. Whether dominated by dusty AGN, compact star-formation, or both, the high masses/luminosities and remarkable abundance of LRDs implies a dominant mode of early galaxy/SMBH growth.
AB - JWST has revealed a population of compact and extremely red galaxies at $z>4$, which likely host active galactic nuclei (AGN). We present a sample of 434 ``little red dots'' (LRDs), selected from the 0.54 deg$^2$ COSMOS-Web survey. We fit galaxy and AGN SED models to derive redshifts and physical properties; the sample spans $z\sim5$-$9$ after removing brown dwarf contaminants. We consider two extreme physical scenarios: either LRDs are all AGN, and their continuum emission is dominated by the accretion disk, or they are all compact star-forming galaxies, and their continuum is dominated by stars. If LRDs are AGN-dominated, our sample exhibits bolometric luminosities $\sim10^{45-47}$ erg\,s$^{-1}$, spanning the gap between JWST AGN in the literature and bright, rare quasars. We derive a bolometric luminosity function (LF) $\sim100$ times the (UV-selected) quasar LF, implying a non-evolving black hole accretion density of $\sim10^{-4}$ M$_\odot$ yr$^{-1}$ Mpc$^{-3}$ from $z\sim2$-$9$. By contrast, if LRDs are dominated by star formation, we derive stellar masses $\sim10^{8.5-10}\,M_\odot$. MIRI/F770W is key to deriving accurate stellar masses; without it, we derive a mass function inconsistent with $\Lambda$CDM. The median stellar mass profile is broadly consistent with the maximal stellar mass surface densities seen in the nearby universe, though the most massive $\sim50$\% of objects exceed this limit, requiring substantial AGN contribution to the continuum. Nevertheless, stacking all available X-ray, mid-IR, far-IR/sub-mm, and radio data yields non-detections. Whether dominated by dusty AGN, compact star-formation, or both, the high masses/luminosities and remarkable abundance of LRDs implies a dominant mode of early galaxy/SMBH growth.
KW - Astrophysics - Astrophysics of Galaxies
M3 - Article
SN - 2331-8422
JO - arXiv.org
JF - arXiv.org
ER -