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1. Identification of Candidate Halos Hosting Massive Black Hole Seeds in the Renaissance Simulations with Support Vector Machines

   https://doi.org/10.3847/1538-4357/ae64fa  

   Pries, Brandon; Wise, John H (June 2026, The Astrophysical Journal)

   Abstract The nature of the origins of supermassive black holes remains uncertain. Multiple possible seeding pathways have been proposed across a variety of mass scales, each with their own strengths and weaknesses. One such channel is a direct collapse black hole (DCBH), thought to form from the deaths of supermassive stars in pristine atomic cooling halos in the early Universe. In this work, we investigate the ability to identify halos likely to form a DCBH based on their properties using a support vector machine (SVM). We implement multiple methods to improve the accuracy of the model, including selecting subsets of critical features and optimizing SVM hyperparameters. We find that our best model requires quantities relevant to star formation, such as the metallicity, incident flux of Lyman–Werner radiation, and halo stellar mass. The SVMs produced from this work can serve as probabilistic and holistic seeding prescriptions for DCBHs in cosmological simulations. 

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2. A search for high-redshift direct-collapse black hole candidates in the PEARLS north ecliptic pole field

   https://doi.org/10.1051/0004-6361/202347724  

   Nabizadeh, Armin; Zackrisson, Erik; Pacucci, Fabio; Peter_Maksym, Walter; Li, Weihui; Civano, Francesca; Cohen, Seth H; D’Silva, Jordan_C J; Koekemoer, Anton M; Summers, Jake; et al (March 2024, Astronomy & Astrophysics)

   Direct-collapse black holes (DCBHs) of mass ∼10⁴ − 10⁵ M_⊙that form in HI-cooling halos in the early Universe are promising progenitors of the ≳10⁹ M_⊙supermassive black holes that fuel observedz ≳ 7 quasars. Efficient accretion of the surrounding gas onto such DCBH seeds may render them sufficiently bright for detection with the JWST up toz ≈ 20. Additionally, the very steep and red spectral slope predicted across the ≈1 − 5 μm wavelength range of the JWST/NIRSpec instrument during their initial growth phase should make them photometrically identifiable up to very high redshifts. In this work, we present a search for such DCBH candidates across the 34 arcmin²in the first two spokes of the JWST cycle-1 PEARLS survey of the north ecliptic pole time-domain field covering eight NIRCam filters down to a maximum depth of ∼29 AB mag. We identify two objects with spectral energy distributions consistent with theoretical DCBH models. However, we also note that even with data in eight NIRCam filters, objects of this type remain degenerate with dusty galaxies and obscured active galactic nuclei over a wide range of redshifts. Follow-up spectroscopy would be required to pin down the nature of these objects. Based on our sample of DCBH candidates and assumptions on the typical duration of the DCBH steep-slope state, we set a conservative upper limit of ≲5 × 10⁻⁴comoving Mpc⁻³(cMpc⁻³) on the comoving density of host halos capable of hosting DCBHs with spectral energy distributions similar to the theoretical models atz ≈ 6 − 14. 

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3. Black Hole Growth, Baryon Lifting, Star Formation, and IllustrisTNG

   https://doi.org/10.3847/1538-4357/ad0039  

   Voit, G Mark; Oppenheimer, Benjamin D; Bell, Eric F; Terrazas, Bryan; Donahue, Megan (December 2023, The Astrophysical Journal)

   Abstract Quenching of star formation in the central galaxies of cosmological halos is thought to result from energy released as gas accretes onto a supermassive black hole. The same energy source also appears to lower the central density and raise the cooling time of baryonic atmospheres in massive halos, thereby limiting both star formation and black hole growth, by lifting the baryons in those halos to greater altitudes. One predicted signature of that feedback mechanism is a nearly linear relationship between the central black hole’s mass (M_BH) and the original binding energy of the halo’s baryons. We present the increasingly strong observational evidence supporting a such a relationship, showing that it extends up to halos of massM_halo∼ 10¹⁴M_⊙. We then compare current observational constraints on theM_BH–M_halorelation with numerical simulations, finding that black hole masses in IllustrisTNG appear to exceed those constraints atM_halo< 10¹³M_⊙and that black hole masses in EAGLE fall short of observations atM_halo∼ 10¹⁴M_⊙. A closer look at IllustrisTNG shows that quenching of star formation and suppression of black hole growth do indeed coincide with black hole energy input that lifts the halo’s baryons. However, IllustrisTNG does not reproduce the observedM_BH–M_halorelation because its black holes gain mass primarily through accretion that does not contribute to baryon lifting. We suggest adjustments to some of the parameters in the IllustrisTNG feedback algorithm that may allow the resulting black hole masses to reflect the inherent links between black hole growth, baryon lifting, and star formation among the massive galaxies in those simulations. 

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4. On the Formation and Interaction of Multiple Supermassive Stars in Cosmological Flows

   https://doi.org/10.3847/1538-4357/ad054a  

   Woods, Tyrone E; Patrick, Samuel; Whalen, Daniel J; Heger, Alexander (December 2023, The Astrophysical Journal)

   Abstract Supermassive primordial stars with masses exceeding ∼10⁵M_⊙that form in atomically cooled halos are the leading candidates for the origin of high-redshift quasars atz> 6. Recent numerical simulations, however, find that multiple accretion disks can form within a halo, each of which can potentially host a supermassive star. We investigate the formation and evolution of secondary supermassive stars in atomically cooled halos, including strong variations in their accretion histories driven by gravitational interactions between their disks and those surrounding the primary supermassive stars in each halo. We find that all secondary disks produce long-lived supermassive stars under sustained rapid accretion. We also find, however, that the majority of secondary supermassive stars do undergo at least one protracted quiescent accretion phase, during which time they thermally relax and may become powerful sources of ionizing feedback. In many halos, the two satellite disks collide, suggesting that the two stars can come into close proximity. This may induce additional mass exchange between them, leading to a great diversity of possible outcomes. These range from coevolution as main-sequence stars to main sequence—black hole pairs and black hole—black hole mergers. We discuss the likely outcome for these binary interactions based on the evolutionary state of both supermassive stars at the end of our simulations, as well as prospects for their future detection by current and next-generation facilities. 

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5. The X–shooter/ALMA Sample of Quasars in the Epoch of Reionization. II. Black Hole Masses, Eddington Ratios, and the Formation of the First Quasars

   https://doi.org/10.3847/1538-4357/ac9626  

   Farina, Emanuele Paolo; Schindler, Jan-Torge; Walter, Fabian; Bañados, Eduardo; Davies, Frederick B.; Decarli, Roberto; Eilers, Anna-Christina; Fan, Xiaohui; Hennawi, Joseph F.; Mazzucchelli, Chiara; et al (December 2022, The Astrophysical Journal)

   Abstract We present measurements of black hole masses and Eddington ratios (λ_Edd) for a sample of 38 bright (M₁₄₅₀< −24.4 mag) quasars at 5.8 ≲z≲ 7.5, derived from Very Large Telescope/X–shooter near–IR spectroscopy of their broad Civand Mgiiemission lines. The black hole masses (on average,M_BH∼ 4.6 × 10⁹M_⊙) and accretion rates (0.1 ≲λ_Edd≲ 1.0) are broadly consistent with that of similarly luminous 0.3 ≲z≲ 2.3 quasars, but there is evidence for a mild increase in the Eddington ratio abovez≳ 6. Combined with deep Atacama Large Millimeter/submillimeter Array (ALMA) observations of the [CII] 158μm line from the host galaxies and VLT/MUSE investigations of the extended Lyαhalos, this study provides fundamental clues to models of the formation and growth of the first massive galaxies and black holes. Compared to local scaling relations,z≳ 5.7 black holes appear to be over-massive relative to their hosts, with accretion properties that do not change with host galaxy morphologies. Assuming that the kinematics of theT∼ 10⁴K gas, traced by the extended Lyαhalos, are dominated by the gravitational potential of the dark matter halo, we observe a similar relation between black hole mass and circular velocity as reported forz∼ 0 galaxies. These results paint a picture where the first supermassive black holes reside in massive halos atz≳ 6 and lead the first stages of galaxy formation by rapidly growing in mass with a duty cycle of order unity. The duty cycle needs to drastically drop toward lower redshifts, while the host galaxies continue forming stars at a rate of hundreds of solar masses per year, sustained by the large reservoirs of cool gas surrounding them. 

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