Constraining AGN accretion physics with black hole mass-luminosity scaling relations

F. Fiore, M. Gaspari, S. Puccetti, M. Bischetti, C. Feruglio, E. Piconcelli

First listed 2026-06-03 | Last updated 2026-06-02

Abstract

We test how supermassive black holes are fed by combining new black hole mass-luminosity relations with physically motivated feeding models. We build a uniform sample of 1729 unobscured blue quasars at z>2 by cross-matching SDSS DRE16 with eROSITA, and augment it with hyperluminous quasars (WISSH, HYPERION) plus 49 JWST broad-line AGN at z>3.5. We find for the SDSS-eROSITA sample of blue quasars a near-linear scaling of bolometric luminosity with mass (slope 0.91+/-0.01) and a shallower hard-X-ray trend (slope 0.73+/-0.01). Classical hot-mode (Bondi) accretion underpredicts the observed luminosities by about 2 dex at the high-mass end and is inconsistent with the measured slopes. In contrast, Chaotic Cold Accretion (CCA) - in which multiphase gas condenses, collides, and rains onto the nucleus - consistently reproduces both the normalization and the near-linear slope expected from halo thermodynamics. The shallower X-ray relation points to a decreasing coronal power fraction with black hole mass. JWST broad-line AGN frequently appear X-ray weak or Halpha enhanced. The latter case can be due to contributions from collisional ionization and photoionization from star-formation to the broad Halpha emission, leading to overestimate AGN luminosities and black hole masses. In the former case, the X-ray weakness is consistent with coronal shielding or anisotropy at high accretion rates. Overall, the data favor CCA-driven, self-regulated feeding over local spherical capture across the BH mass range 1E7-1E10 solar masses, and motivate extending these tests to lower masses and higher redshifts.

Short digest

This paper tests black-hole feeding models against new mass-luminosity scalings built from a uniform sample of 1,729 unobscured SDSS-eROSITA blue quasars, supplemented by hyperluminous WISSH and HYPERION quasars and 49 JWST broad-line AGN at z>3.5. The key result is that bolometric luminosity scales nearly linearly with black-hole mass, while the hard-X-ray relation is significantly shallower; classical Bondi-like hot accretion misses both the slope and normalization, underpredicting the most massive systems by about 2 dex, whereas Chaotic Cold Accretion reproduces the observed trend across 10^7-10^10 solar masses. That makes the scaling relation itself a physically discriminating test, pointing to self-regulated multiphase fueling rather than local spherical capture as the dominant mode of SMBH growth over a broad mass range. For the JWST broad-line AGN, the paper also argues that apparent X-ray weakness and Halpha enhancement can bias inferred AGN luminosities and virial black-hole masses, which matters directly for interpreting early black-hole growth claims.

Key figures to inspect

• Figure 1. This is the essential overview figure because it puts the bolometric and 2-10 keV luminosity versus black-hole mass relations side by side for all major samples and directly overlays the Bondi and CCA model expectations. It shows the paper’s core quantitative claim: a near-linear bolometric slope for the SDSS-eROSITA blue quasars, a shallower X-ray slope, Bondi underprediction at high mass, and broad consistency with CCA across the full dynamic range.
• Figure 3. This figure is the best companion to Figure 1 because it helps explain why the X-ray relation is shallower than the bolometric one. The luminosity-distribution tails and the X-ray-to-bolometric correction as a function of source properties, with black-hole mass encoded, are where the paper’s inference about a declining coronal power fraction with increasing mass becomes most concrete.
• Figure 4. This is the most important figure for the JWST-facing readership because it compares X-ray luminosity directly against broad Halpha luminosity for SDSS-eROSITA quasars, WISSH objects, and z>4 JWST AGN. It makes visible the two caveat-driving populations emphasized in the abstract, namely X-ray-weak and Halpha-enhanced broad-line AGN, and therefore shows why some JWST virial masses and AGN luminosities may be overestimated.
• Figure 2. Although less central than Figures 1, 3, and 4, this figure adds physical context by linking CIV velocity shifts, excess line width, and equivalent width to accretion-related wind phenomenology across the SDSS-eROSITA, WISSH, and HYPERION samples. It is useful for readers who want to connect the mass-luminosity scalings to the broader high-accretion, strong-outflow regime that may also underpin coronal shielding or anisotropy in the most luminous systems.