More Like this

1. Growth of massive black holes in FFB galaxies at cosmic dawn

   https://doi.org/10.1051/0004-6361/202452393  

   Dekel, Avishai; Stone, Nicholas C; Chowdhury, Dhruba Dutta; Gilbaum, Shmuel; Li, Zhaozhou; Mandelker, Nir; van_den_Bosch, Frank C (March 2025, Astronomy & Astrophysics)

   Aims.The scenario of feedback-free starbursts (FFB), which predicts excessively bright galaxies at cosmic dawn as observed using JWST, may provide a natural setting for black hole (BH) growth. This involves the formation of intermediate-mass seed BHs and their runaway mergers into super-massive BHs with high BH-to-stellar mass ratios and low Active Galactic Nucleus (AGN) luminosities. Methods.We present a scenario of merger-driven BH growth in FFB galaxies and study its feasibility. Results.Black hole seeds form within the building blocks of the FFB galaxies, namely, thousands of compact star clusters, each starbursting in a free-fall time of a few million years before the onset of stellar and supernova feedback. The BH seeds form by rapid core collapse in the FFB clusters, in a few free-fall times, which is sped up by the migration of massive stars due to the young, broad stellar mass function and stimulated by a “gravo-gyro” instability due to internal cluster rotation and flattening. BHs of ∼10⁴ M_⊙are expected in ∼10⁶ M_⊙FFB clusters within sub-kiloparsec galactic disks atz​ ∼ ​10. The BHs then migrate to the galaxy center by dynamical friction, hastened by the compact FFB stellar galactic disk configuration. Efficient mergers of the BH seeds will produce ∼10^6 − 8 M_⊙BHs with a BH-to-stellar mass ratio ∼0.01 byz​ ∼ ​4 − 7, as observed. The growth of the central BH by mergers can overcome the bottleneck introduced by gravitational wave recoils if the BHs inspiral within a relatively cold disk or if the escape velocity from the galaxy is boosted by a wet compaction event. Such events, common in massive galaxies at high redshifts, can also help by speeding up the inward BH migration and by providing central gas to assist with the final parsec problem. Conclusions.The cold disk version of the FFB scenario provides a feasible route for the formation of supermassive BHs. 

   more » « less
2. Multiwavelength Constraints on the Local Black Hole Occupation Fraction

   https://doi.org/10.3847/1538-4357/ad94d9  

   Burke, Colin J; Natarajan, Priyamvada; Baldassare, Vivienne F; Geha, Marla (December 2024, The Astrophysical Journal)

   Abstract The fraction of dwarf galaxies hosting central, intermediate-mass black holes (IMBHs) at low redshifts is an important observational probe of black hole seeding at high redshift. Detections of nuclear accretion signatures in dwarf galaxies provides strong evidence for the presence of these IMBHs. We develop a Bayesian model to infer the black hole occupation fraction assuming a broken power-law Eddington ratio distribution function. Our approach accounts for nondetections, incompleteness, and contamination from star-forming-related emission. We apply this model to galaxies with X-ray data from the Chandra Source Catalog at distances <50 Mpc, radio data from the Very Large Array Sky Survey at <50 Mpc, and optical variability data from the Palomar Transient Factory atz< 0.055. We find a black hole occupation fraction of at least 90% at stellar masses ofM_⋆= 10⁸M_⊙and at least 39% atM_⋆= 10⁷M_⊙(95% confidence intervals). We show the resulting black hole mass function. These constraints on the IMBH population have implications for the Laser Interferometer Space Antenna mission and for cosmological models of black hole seeding and growth. We also constrain the extremely low-luminosity end (L_bol≲ 10⁴⁰erg s⁻¹) of the active galactic nucleus (AGN) luminosity functions atz= 0. Our AGN luminosity functions are broadly consistent with an extrapolation of the shallow slope of the AGN luminosity functions from previous work. 

   more » « less
3. Tracking the Assembly of Supermassive Black Holes: A Comparison of Diverse Models across Cosmic Time

   https://doi.org/10.3847/1538-4357/ae2fb1  

   Porras-Valverde, Antonio J; Ricarte, Angelo; Natarajan, Priyamvada; Somerville, Rachel S; Gabrielpillai, Austen; Yung, L_Y Aaron (February 2026, The Astrophysical Journal)

   Abstract Galaxies grow alongside central supermassive black holes (SMBHs) through fueling and feedback. However, the origins of this coevolution remain unclear and vary across modeling frameworks. Using semianalytic models (SAMs), we trace SMBH mass assembly acrossM_BH ∼ 10⁶⁻¹⁰M_⊙. We find significant discrepancies between observations and physics-based models of the local black hole mass function (BHMF), likely from differences in the stellar mass function and scaling relations used to infer the BHMF. Most physics-based models agree atz ∼ 1–4 and broadly match the JWST broad-line active galactic nucleus (AGN) BHMFs atz = 4–5. These models also reproduce the observed bolometric AGN luminosity evolution, except the SAMDark Sage, which predicts an excess. Interestingly, this pronounced “knee” in the bolometric AGN luminosity function predicted byDark SagearoundL_bol ∼ 10⁴⁶erg s⁻¹is consistent with the inferred abundance and luminosity of “little red dots” atz = 5–6, under the assumption that they are powered entirely by AGN activity. In contrast to other models,Dark Sagedeploys multiple growth channels for SMBHs that include mergers, hot-mode accretion, merger-driven cold-accretion, and secular-instability-driven accretion. We analyze the black hole mass buildup and accretion histories inDark Sage, which, unlike other models, also allows for super-Eddington accretion, and we find that, on average, SMBHs primarily grow through secular disk instabilities and merger-driven cold gas accretion modes. We also find that black hole mergers contribute the majority of the growth of ∼60% of the total mass budget only for the most massive SMBHs byz= 0. 

   more » « less
4. A CEERS Discovery of an Accreting Supermassive Black Hole 570 Myr after the Big Bang: Identifying a Progenitor of Massive z > 6 Quasars

   https://doi.org/10.3847/2041-8213/ace619  

   Larson, Rebecca L; Finkelstein, Steven L; Kocevski, Dale D; Hutchison, Taylor A; Trump, Jonathan R; Arrabal_Haro, Pablo; Bromm, Volker; Cleri, Nikko J; Dickinson, Mark; Fujimoto, Seiji; et al (August 2023, The Astrophysical Journal Letters)

   Abstract We report the discovery of an accreting supermassive black hole atz= 8.679. This galaxy, denoted here as CEERS_1019, was previously discovered as a Lyα-break galaxy by Hubble with a Lyαredshift from Keck. As part of the Cosmic Evolution Early Release Science (CEERS) survey, we have observed this source with JWST/NIRSpec, MIRI, NIRCam, and NIRCam/WFSS and uncovered a plethora of emission lines. The Hβline is best fit by a narrow plus a broad component, where the latter is measured at 2.5σwith an FWHM ∼1200 km s⁻¹. We conclude this originates in the broadline region of an active galactic nucleus (AGN). This is supported by the presence of weak high-ionization lines (N V, N IV], and C III]), as well as a spatial point-source component. The implied mass of the black hole (BH) is log (M_BH/M_⊙) = 6.95 ± 0.37, and we estimate that it is accreting at 1.2 ± 0.5 times the Eddington limit. The 1–8μm photometric spectral energy distribution shows a continuum dominated by starlight and constrains the host galaxy to be massive (log M/M_⊙∼9.5) and highly star-forming (star formation rate, or SFR ∼ 30 M_⊙yr⁻¹; log sSFR ∼ − 7.9 yr⁻¹). The line ratios show that the gas is metal-poor (Z/Z_⊙∼ 0.1), dense (n_e∼ 10³cm⁻³), and highly ionized (logU∼ − 2.1). We use this present highest-redshift AGN discovery to place constraints on BH seeding models and find that a combination of either super-Eddington accretion from stellar seeds or Eddington accretion from very massive BH seeds is required to form this object. 

   more » « less
5. Connecting Cores and Black Hole Dynamics across Scales: From Globular Clusters to Massive Ellipticals

   https://doi.org/10.3847/2041-8213/ae1233  

   Kremer, Kyle; Weatherford, Newlin C; Hopkins, Philip F; Rui, Nicholas Z; Ye, Claire S (October 2025, The Astrophysical Journal Letters)

   Abstract The centers of massive elliptical galaxies exhibit a wide range in density profiles, from central cusps to resolved cores with order kiloparsec sizes. The cored ellipticals have been linked to the presence of supermassive black hole binaries that excavate their hosts’ central stellar populations through three-body encounters. This connection between cores and black holes similarly operates in globular clusters, which also exhibit a bimodality in cored and core-collapsed architectures, rich and depleted, respectively, in stellar black holes. We report new estimates of the total black hole mass in 25 Galactic globular clusters based on a suite of roughly 150 Monte CarloN-body simulations that fit observed surface brightness and velocity dispersion profiles. We show that both globular clusters and massive elliptical galaxies individually exhibit strong correlations between total black hole mass (M_•) and core radius (r_c) and that these individual relations share a common power-law exponent to within 1σstatistical precision: $M_{•}\sim r_c^{1.3}$ . The individual relations appear to be offset, suggesting swarms of stellar black holes scour globular cluster cores more efficiently than lone supermassive black holes scour the cores of massive ellipticals. Yet the shared basis of core scouring via black hole binaries hints at a unifiedM_•–r_cconnection across over 10 orders of magnitude inM_•. Our findings imply core radius measurements may offer a powerful observational constraint on black hole merger rates, from kilohertz sources detectable by LIGO/Virgo/KAGRA formed in globular clusters to millihertz and nanohertz sources formed in massive elliptical galaxies. 

   more » « less