Dark Matter Halo--Galaxy--Supermassive Black Hole Connection from z=0-10

Abstract

I developed Trinity, a flexible empirical model that self-consistently infers the statistical connection between dark matter haloes, galaxies, and supermassive black holes (SMBHs). Trinity is constrained by galaxy observables from 0 < z < 13 (galaxies’ stellar mass functions, specific and cosmic SFRs, quenched fractions, and UV luminosity functions) and SMBH observables from 0 < z < 6.5 (quasar luminosity functions, quasar probability distribution functions, active black hole mass functions, local SMBH mass–bulge mass relations, and the observed SMBH mass distributions of high redshift bright quasars). The model includes full treatment of observational systematics (e.g., AGN obscuration and errors in stellar masses). From these data, Trinity infers the average SMBH mass, SMBH accretion rate, merger rate, and Eddington ratio distribution as functions of halo mass, galaxy stellar mass, and redshift. Key findings include: 1) the normalization and the slope of the SMBH mass–bulge mass relation increases mildly from z = 0 to z = 10; At z ∼ 6, the intrinsic M•–M∗ relation for all SMBHs is slightly steeper than the z = 0 scaling, with a similar normalization at M∗ ∼ 1011M⊙. We also predict the M•–M∗ relation for z = 6 bright quasars selected by different bolometric luminosity thresholds, finding very good agreement with observations. 3) the new JWST AGNs at 7 ≲ z ≲ 11 are overmassive compared to the intrinsic SMBH mass–galaxy mass relation from Trinity, but they are still broadly consistent with Trinity predictions for flux limited samples that favors the detection for overmassive SMBHs due to higher luminosities. 2) The best-fitting AGN radiative+kinetic efficiency is ∼ 7%, but can range from ∼ 0.05 − 0.10 with alternative input assumptions; 3) AGNs show downsizing, i.e., the Eddington ratios of more massive SMBHs start to decrease earlier than those of lower-mass objects; 4) The average ratio between average SMBH accretion rate and SFR is ∼ 10−3 for low-mass galaxies, which are primarily star-forming. This ratio increases to ∼ 10^−1 for the most massive haloes below z ∼ 1, where star formation is quenched but SMBHs continue to accrete. 5) The normalization of QLF increases by ∼ 3−4 dex from z ∼ 10 to z ∼ 4, due to the fast mass build-up of different SMBH populations; 6) From z ∼ 4 to z ∼ 1, less massive galaxies and SMBHs make up bigger and bigger fractions of QLFs, due to the AGN downsizing effect; 3) At z ∼ 0, massive haloes/galaxies/SMBHs are responsible for most bright quasars due to low Eddington ratios among all SMBHs; 4) The bright ends of quasar luminosity functions (QLFs) are dominated by SMBHs that are at least 0.3 dex over-massive relative to the median SMBH mass–galaxy mass relation; 7) QLFs at z ∼ 6 − 7 are dominated by SMBHs accreting at Eddington ratios 0.1 < η_rad < 1, but super-Eddington AGNs contribute more significantly to QLFs towards z ∼ 9 − 10. 8) The number of SMBHs with M• > 10^9M⊙ in the observable Universe increases by five orders of magnitude from z ∼ 10 to z ∼ 2, and by another factor of ∼ 3 from z ∼ 2 to z = 0; 9) The M• > 10^9 or 10^10M⊙ SMBHs at z ∼ 6 live in haloes with ∼ (2−3) or (3−5)×10^12M⊙; 10) z = 6 − 10 quasar luminosity functions from wide area surveys by, e.g., Roman and Euclid,will reduce uncertainties in the Trinity prediction of the z = 6 − 10 SMBH mass–galaxy mass relation by up to ∼ 0.5 dex. 11) average SMBH merger rate increases monotonically as a function of halo/galaxy/SMBH mass at a fixed redshift, and remains negligible compared to SMBH accretion rate in terms of both instantaneous and cumulative contributions to total SMBH growth. 12) combined with a post-processing scheme of SMBH binary evolution, Trinity predicts a gravitational wave background strain of ∼ (5 − 8) × 10^−16 at the frequency of 1 yr^−1, which is roughly 1/3 of the recent detection value from pulsar timing array observations.