Supermassive black holes with higher Eddington ratios preferentially form in gas-rich galaxies

Abstract

The Eddington ratio (${\lambda }_{\mathrm{Edd}}$) of supermassive black holes (SMBHs) is a fundamental parameter that governs the cosmic growth of SMBHs. Although gas mass accretion onto SMBHs is sustained when they are surrounded by large amounts of gas, little is known about the molecular content of galaxies, particularly those hosting super-Eddington SMBHs (${\lambda }_{\mathrm{Edd}}>1$: the key phase of SMBH growth). Here, we compiled reported optical and ${}^{12}$CO(1--0) data of local quasars to characterize their hosts. We found that higher ${\lambda }_{\mathrm{Edd}}$ SMBHs tend to reside in gas rich (i.e., high gas mass to stellar mass fraction = $f_{\mathrm{gas}}$) galaxies. We used two methods to make this conclusion: one uses black hole mass as a surrogate for stellar mass by assuming a local co-evolutionary relationship, and the other directly uses stellar masses estimated from near-infrared observations. The $f_{\mathrm{gas}}$--${\lambda }_{\mathrm{Edd}}$ correlation we found concurs with the cosmic decreasing trend in ${\lambda }_{\mathrm{Edd}}$, as cold molecular gas is primarily consumed by star formation. This correlation qualitatively matches predictions of recent semi-analytic models about the cosmic downsizing of SMBHs as well. As the gas mass surface density would eventually be a key parameter controlling mass accretion, we need high-resolution observations to identify further differences in the molecular properties around super-Eddington and sub-Eddington SMBHs.

6 pages, 4 figures, accepted for publication in the Publications of the Astronomical Society of Japan (PASJ) Letter

References in corpus (14)

• Cosmic Star Formation History
• An 800-million-solar-mass black hole in a significantly neutral Universe at redshift 7.5
• Toward the Standard Population Synthesis Model of the X-Ray Background: Evolution of X-Ray Luminosity and Absorption Functions of Active Galactic Nuclei Including Compton-Thick Populations
• Biases in Virial Black Hole Masses: An SDSS Perspective
• The Radius-Luminosity Relationship for Active Galactic Nuclei: The Effect of Host-Galaxy Starlight on Luminosity Measurements
• Supermassive Black Holes with High Accretion Rates in Active Galactic Nuclei. IV. H$\beta$ Time Lags and Implications for Super-Eddington Accretion
• Coevolution of Supermassive Black Holes and Circumnuclear Disks
• Integral field spectroscopy of nearby QSOs: I. ENLR size-luminosity relation, ongoing star formation & resolved gas-phase metallicities
• Dense Molecular Gas and the Role of Star Formation in the Host Galaxies of Quasi-Stellar Objects
• Molecular gas in nearby low-luminosity QSO host galaxies
• Starbursts and torus evolution in AGN
• Integral field spectroscopy of nearby QSOs II. The molecular gas content and condition for star formation
• Physical properties of the first quasars
• Anti-hierarchical evolution of the Active Galactic Nucleus space density in a hierarchical universe

Cited by in corpus (3)

• Subaru High-z Exploration of Low-Luminosity Quasars (SHELLQs) VIII. A less biased view of the early co-evolution of black holes and host galaxies
• AGN Feedback and Star Formation of Quasar Host Galaxies: Insights from the Molecular Gas
• Rapid Black Hole Spin-down by Thick Magnetically Arrested Disks