Supermassive black holes with billion solar masses are in place already within the first Gyr, however, their origin and growth in such a short lapse of time is extremely challenging to understand. Here, we discuss the formation paths of early black-hole seeds, showing the limits of light black-hole seeds from stellar origin and the expected characteristics of heavy/massive black-hole seeds originated by gas direct collapse in peculiar primordial conditions. To draw conclusions on the possible candidates and the role of the ambient medium, we use results from N-body hydrodynamic simulations including atomic and molecular non-equilibrium abundance calculations, cooling, star formation, feedback mechanisms, stellar evolution, metal spreading of several heavy elements from SNII, AGB and SNIa, and multifrequency radiative transfer over 150 frequencies coupled to chemistry and SED emission for popII-I and popIII stellar sources. Standard stellar-origin light black holes are unlikely to be reliable seeds of early supermassive black holes, because, under realistic assumptions, they cannot grow significantly in less than a billion years. Alternatively, massive black-hole seeds might originate from direct collapse of pristine gas in primordial quiescent mini-haloes that are exposed to stellar radiation from nearby star forming regions. The necessary conditions required to form these heavy seeds must be complemented with information on the complex features of local environments and the fine balance between chemistry evolution and radiative transfer.
The properties of primordially-seeded black holes and their hosts in the first billion years: implications for JWST
David A. Dunlap Department of Astronomy and Astrophysics, University of Toronto（多伦多大学戴维·A·邓普尔天文与天体物理系）；Kapteyn Astronomical Institute, University of Groningen（格罗宁根大学卡普坦天文研究所）；Kavli Institute for Cosmology, University of Cambridge（剑桥大学卡弗里宇宙学研究所）；Cavendish Laboratory, University of Cambridge（剑桥大学卡文迪许实验室）；Department of Physics and Astronomy, University College London（伦敦大学学院物理与天文学系）
The existence of black holes in the intermediate mass interval between one hundred and ten thousand solar masses, filling the gap between the stellar and the supermassive black holes is a key prediction to explain the origin of luminous QSOs at redshifts as large as seven. There is a sheer difficulty in forming giant black holes of billion suns in less than one billion years. This has led to the concept of seed black holes. They are high redshift intermediate mass black holes that formed during cosmic dawn. Seeds are a transient population, which later grew massive through episodes of accretio…
Observational constraints on the birth and early evolution of massive black holes (BHs) come from two extreme regimes. At high redshift, quasars signal the rapid growth of billion-solar-mass BHs and indicate that these objects began remarkably heavy and/or accreted mass at rates above the Eddington limit. At low redshift, the smallest nuclear BHs known are found in dwarf galaxies and provide the most concrete limits on the mass of BH seeds. Here we review current observational work in these fields that together are critical for our understanding of the origin of massive BHs in the Universe.
Mass accretion by black holes (BHs) is typically capped at the Eddington rate, when radiation's push balances gravity's pull. However, even exponential growth at the Eddington-limited e-folding time t_E ~ few x 0.01 billion years, is too slow to grow stellar-mass BH seeds into the supermassive luminous quasars that are observed when the universe is 1 billion years old. We propose a dynamical mechanism that can trigger supra-exponential accretion in the early universe, when a BH seed is trapped in a star cluster fed by the ubiquitous dense cold gas flows. The high gas opacity traps the accretio…
We study the early growth of massive seed black holes (BHs) via accretion in protogalactic nuclei where the stellar bulge component is assembled, performing axisymmetric two-dimensional radiation hydrodynamical simulations. We find that when a seed BH with $M_\bullet \sim 10^5~M_\odot$ is embedded in dense metal-poor gas ($Z=0.01~Z_\odot$) with a density of $\gtrsim 100~{\rm cm}^{-3}$ and bulge stars with a total mass of $M_\star \gtrsim 100~M_\bullet$, a massive gaseous disk feeds the BH efficiently at rates of $\gtrsim 0.3-1~M_\odot~{\rm yr}^{-1}$ and the BH mass increases nearly tenfold wit…
First results of AMBRA: Abundant Seeds and Early Mergers as a Pathway to the First Massive Black Holes
Carnegie Mellon University（卡内基梅隆大学）；University of Virginia（弗吉尼亚大学）；Virginia Institute for Theoretical Astronomy, University of Virginia（弗吉尼亚大学理论天体物理研究所）；University of Florida（佛罗里达大学）；University of California, Riverside（加州大学河滨分校）；Harvard-Smithsonian Center for Astrophysics（哈佛-史密森尼天体物理中心）
Black Hole merger rates in the first billion years in light of JWST data
Kapteyn Astronomical Institute, University of Groningen（格罗宁根大学卡普坦天文研究所）；Departamento de Astronomía Cerro Calan, Universidad de Chile（智利大学塞罗卡兰天文学系）；Millennium Nucleus on Transversal Research and Technology to Explore Supermassive Black Holes (TITANS)（探索超大质量黑洞跨学科研究与技术千年核（TITANS））；David A. Dunlap Department of Astronomy and Astrophysics, University of Toronto（多伦多大学大卫A.邓普林天文学与天体物理学系）；Departemen Fisika, FMIPA, Universitas Indonesia（印度尼西亚大学理学院物理系）；LUX, Observatoire de Paris, Universitè PSL, Sorbonne Universitè, CNRS（巴黎天文台卢克斯实验室，巴黎文理研究大学，索邦大学，法国国家科学研究中心）
A Dark-matter Origin of Little Red Dots: Early Seeding and Super-Bondi Accretion
Peking University（北京大学）；Kavli Institute for Astronomy and Astrophysics, Peking University（北京大学科维理天文与天体物理研究所）；Beijing Normal University（北京师范大学）；School of Physics and Astronomy, Beijing Normal University（北京师范大学物理学院）；University of Chinese Academy of Sciences（中国科学院大学）；School of Astronomy and Space Science, University of Chinese Academy of Sciences（中国科学院大学天文与空间科学学院）
The existence of $\gtrsim10^9M_\odot$ supermassive black holes (SMBHs) at redshift $z>6$ raises the problem of how such SMBHs can grow up within the cosmic time ($<1$\,Gyr) from small seed BHs. In this letter, we use the observations of $14$ Quasars at $z>6.5$ with mass estimates to constrain their seeds and early growth, by self-consistently considering the spin evolution and the possibility of super-Eddington accretion. We find that spin plays an important role in the growth of early SMBHs, and the constraints on seed mass and super-Eddington accretion fraction strongly depend on the assumed…
The detection of quasars at $z>6$ unveils the presence of supermassive black holes (BHs) of a few billion solar masses. The rapid formation process of these extreme objects remains a fascinating and open issue. Such discovery implies that seed black holes must have formed early on, and grown via either rapid accretion or BH/galaxy mergers. In this theoretical review, we discuss in detail various BH seed formation mechanisms and the physical processes at play during their assembly. We discuss the three most popular BH formation scenarios, involving the (i) core-collapse of massive stars, (ii) d…
The paper examines the early growth of supermassive black holes (SMBHs) in cosmological hydrodynamic simulations with different BH seeding scenarios. Employing the constrained Gaussian realization, we reconstruct the initial conditions in the large-volume BlueTides simulation and run them to $z=6$ to cross-validate that the method reproduces the first quasars and their environments. Our constrained simulations in a volume of $(15\, h^{-1}{\rm Mpc})^3$ successfully recover the evolution of large-scale structure and the stellar and BH masses in the vicinity of a $\sim10^{12}\, M_{\odot}$ halo wh…
Massive black holes (BHs) inhabit local galaxies, including the Milky Way and some dwarf galaxies. BH formation, occurring at early cosmic times, must account for the properties of BHs in today's galaxies, notably why some galaxies host a BH, and others do not. We investigate the formation, distribution and growth of BH `seeds' by using the adaptive mesh refinement code Ramses. We develop an implementation of BH formation in dense, low-metallicity environments, as advocated by models invoking the collapse of the first generation of stars, or of dense nuclear star clusters. The seed masses are …
Accretion of stars on massive black holes (MBHs) can feed MBHs and generate tidal disruption events (TDEs). We introduce a new physically motivated model to self-consistently treat TDEs in cosmological simulations, and apply it to the assembly of a galaxy with final mass $3\times 10^{10}\mathrm{\, M}_\odot$ at $z=6$. This galaxy exhibits a TDE rate of $\sim 10^{-5}\mathrm{\, yr}^{-1}$, consistent with local observations but already in place when the Universe was one billion year old. A fraction of the disrupted stars participate in the growth of MBHs, dominating it until the MBH reaches mass $…
In this work we include black hole (BH) seeding, growth and feedback into our semi-analytic galaxy formation model, Delphi. Our model now fully tracks the, accretion- and merger-driven, hierarchical assembly of the dark matter halo, baryonic and BH masses of high-redshift ($z>5$) galaxies. We use a minimal set of mass- and $z$-independent free parameters associated with star formation and BH growth (and feedback) and include suppressed BH growth in low-mass galaxies to explore a number of physical scenarios including: (i) two types of BH seeds (stellar and those from Direct Collapse BH; DCBH);…
Possible formation scenarios of supermassive black holes in the early universe include rapid growth from less massive seed black holes (BHs) via super-Eddington accretion or runaway mergers, yet both of these scenarios would require seed BHs to efficiently sink to and be trapped in the galactic center via dynamical friction. This may not be true for their complicated dynamics in clumpy high-$z$ galaxies. In this work we study this "sinking problem" with state-of-the-art high-resolution cosmological simulations, combined with both direct $N$-body integration of seed BH trajectories and post-pro…
Stellar distances constitute a foundational pillar of astrophysics. The publication of 1.47 billion stellar parallaxes from Gaia is a major contribution to this. Yet despite Gaia's precision, the majority of these stars are so distant or faint that their fractional parallax uncertainties are large, thereby precluding a simple inversion of parallax to provide a distance. Here we take a probabilistic approach to estimating stellar distances that uses a prior constructed from a three-dimensional model of our Galaxy. This model includes interstellar extinction and Gaia's variable magnitude limit. …
The direct collapse model for the formation of massive seed black holes in the early Universe attempts to explain the observed number density of supermassive black holes (SMBHs) at $z \sim 6$ by assuming that they grow from seeds with masses M > 10000 solar masses that form by the direct collapse of metal-free gas in atomic cooling halos in which H2 cooling is suppressed by a strong extragalactic radiation field. The viability of this model depends on the strength of the radiation field required to suppress H2 cooling, $J_{\rm crit}$: if this is too large, then too few seeds will form to expla…
In this white paper we explore the capabilities required to identify and study supermassive black holes formed from heavy seeds ($\mathrm{M_{\bullet}} \sim 10^4 - 10^6 \, \mathrm{M_{\odot}}$) in the early Universe. To obtain an unequivocal detection of heavy seeds we need to probe mass scales of $\sim 10^{5-6} \, \mathrm{M_{\odot}}$ at redshift $z \gtrsim 10$. From this theoretical perspective, we review the observational requirements and how they compare with planned/proposed instruments, in the infrared, X-ray and gravitational waves realms. In conclusion, detecting heavy black hole seeds at…
Intermediate-mass black holes (BHs) in local dwarf galaxies are considered the relics of the early seed BHs. However, their growth might have been impacted by galaxy mergers and BH feedback so that they cannot be treated as tracers of the early seed BH population.
The discovery of a large number of supermassive black holes (SMBH) at redshifts $z > 6$, when the Universe was only 900 million years old, raises the question of how such massive compact objects could form in a cosmologically short time interval. Each of the standard scenarios proposed, involving rapid accretion of seed black holes or black hole mergers, faces severe theoretical difficulties in explaining the short-time formation of supermassive objects. In this work we propose an alternative scenario for the formation of SMBH in the early Universe, in which energy transfer from superconductin…
The SEEDZ Simulations: Methodology and First Results on Massive Black Hole Seeding and Early Galaxy Growth
Maynooth University（梅努斯大学）；Max-Planck-Institut für Astrophysik（马克斯·普朗克天体物理研究所）；University of Cambridge（剑桥大学）；Universität Heidelberg（海德堡大学）；Georgia Institute of Technology（佐治亚理工学院）；University College Cork（科克大学）；Cardiff University（卡迪夫大学）；University of Edinburgh（爱丁堡大学）
Cosmological models predict that galaxies forming in the early Universe experience a chaotic phase of gas accretion and star formation, followed by gas ejection due to feedback processes. Galaxy bulges may assemble later via mergers or internal evolution. Here we present submillimeter observations (with spatial resolution of 700 parsecs) of ALESS 073.1, a starburst galaxy at redshift z~5, when the Universe was 1.2 billion years old. This galaxy's cold gas forms a regularly rotating disk with negligible noncircular motions. The galaxy rotation curve requires the presence of a central bulge in a…
We explore the effect of dust on the growth of seed black holes (BHs) in the early universe. Previous 1D radiation-hydrodynamic (RHD) simulations show that increased radiation pressure on dust further suppresses the accretion rate than the case for the chemically pristine gas. Using the Enzo+Moray code, we perform a suite of 3D RHD simulations of accreting BHs in a dusty interstellar medium (ISM). We use the modified Grackle cooling library to consider dust physics in its non-equilibrium chemistry. The BH goes through an early evolutionary phase, where ionizing BH radiation creates an oscillat…
The James Webb Space Telescope (JWST) will have the sensitivity to detect early low-mass black holes as they transition from "seeds" to supermassive black holes (BHs). Based on the JAGUAR mock catalog of galaxies, we present a clean color selection that takes advantage of the unique UV slope of accreting supermassive black holes with relatively low mass and high accretion rates. We show for a range of host stellar masses that those galaxies hosting $\sim 10^{6} M_{\odot}$ BHs radiating at >10% of their Eddington luminosity separate in color space from inactive systems. Here we propose a set of…
Recent discoveries of super-massive black holes at high redshifts indicate a possible tension with the standard Lambda CDM paradigm of early universe cosmology which has difficulties in explaining the origin of the required nonlinear compact seeds which trigger the formation of these super-massive black holes. Here we show that cosmic string loops which result from a scaling solution of strings formed during a phase transition in the very early universe lead to an additional source of compact seeds. The number density of string-induced seeds dominates at high redshifts and can help trigger the…
Third Generation ground based Gravitational Wave Interferometers, like the Einstein Telescope (ET), Cosmic Explorer (CE), and the Laser Interferometer Space Antenna (LISA) will detectcoalescing binary black holes over a wide mass spectrum and across all cosmic epochs. We track the cosmological growth of the earliest light and heavy seeds that swiftly transit into the supermassive domain using a semi analytical model for the formation of quasars at $z=6.4$, 2 and $0.2$, in which we follow black hole coalescences driven by triple interactions. We find that light seed binaries of several $10^2$ M…
Space telescope observations of massive black holes during their formation may be key to understanding the origin of supermassive black holes and high-redshift quasars. To create diagnostics for their detection and confirmation, we study a simulation of a nascent massive, so-called direct-collapse, black hole that induces a wave of nearby massive metal-free star formation, unique to this seeding scenario and to very high redshifts. Here we describe a series of distinct colors and emission line strengths, dependent on the relative strength of star formation and black hole accretion. We predict …
The direct collapse black hole (DCBH) model attempts to explain the observed number density of supermassive black holes in the early Universe by positing that they grew from seed black holes with masses of $10^{4}$-$10^{5} \: {\rm M_{\odot}}$ that formed by the quasi-isothermal collapse of gas in metal-free protogalaxies cooled by atomic hydrogen emission. For this model to work, H$_{2}$ formation must be suppressed in at least some of these systems by a strong extragalactic radiation field. The predicted number density of DCBH seeds is highly sensitive to the minimum value of the ultraviolet …
We study how statistical properties of supermassive black holes depend on the frequency and conditions for massive seed formation in cosmological simulations of structure formation. We develop a novel method to recalculate detailed growth histories and merger trees of black holes within the framework of the Illustris simulation for several seed formation models, including a physically motivated model where black hole seeds only form in progenitor galaxies that conform to the conditions for direct collapse black hole formation. While all seed models considered here are in a broad agreement with…
We investigate how uncertainties in the chemical and cooling rate coefficients relevant for a metal-free gas influence our ability to determine the critical ultraviolet field strength required to suppress H2 cooling in high-redshift atomic cooling halos. The suppression of H2 cooling is a necessary prerequisite for the gas to undergo direct collapse and form an intermediate mass black hole. These black holes can then act as seeds for the growth of the supermassive black holes (SMBHs) observed at redshifts $z \sim 6$. The viability of this model for SMBH formation depends on the critical ultrav…
Evolution in the measured rest frame ultraviolet spectral slope and ultraviolet to optical flux ratios indicate a rapid evolution in the dust obscuration of galaxies during the first 3 billion years of cosmic time (z>4). This evolution implies a change in the average interstellar medium properties, but the measurements are systematically uncertain due to untested assumptions, and the inability to measure heavily obscured regions of the galaxies. Previous attempts to directly measure the interstellar medium in normal galaxies at these redshifts have failed for a number of reasons with one notab…
Rapid Dark Growth of Seed Black Holes in Self-Interacting Dark Matter
University of Science and Technology of China（中国科学技术大学）；Institute of High Energy Physics, Chinese Academy of Sciences（中国科学院高能物理研究所）；University of Chinese Academy of Sciences（中国科学院大学）
Direct collapse black holes~(BH) are promising candidates for producing massive $z\gtrsim 6$ quasars, but their formation requires fine-tuned conditions. In this work, we use cosmological zoom simulations to study systematically the impact of requiring: 1) low gas angular momentum, and 2) a minimum incident Lyman-Werner~(LW) flux in order to form BH seeds. We probe the formation of seeds (with initial masses of $M_{\rm seed} \sim 10^4$ - $10^6 M_{\odot}/h)$ in halos with a total mass $> 3000\times M_{\mathrm{seed}}$ and a dense, metal poor gas mass $> 5\times M_{\mathrm{seed}}$. We find that t…
Detecting the seed black holes from which quasars formed is extremely challenging; however, those seeds that did not grow into supermassive should be found as intermediate-mass black holes (IMBHs) of 100-10$^5$ M$_{\odot}$ in local dwarf galaxies. The use of deep multiwavelength surveys has revealed that a population of actively accreting IMBHs (low-mass AGN) exists in dwarf galaxies at least out to $z\sim$3. The black hole occupation fraction of these galaxies suggests that the early Universe seed black holes formed from direct collapse of gas, which is reinforced by the possible flattening o…
The first black hole seeds, formed when the Universe was younger than 500 Myr, are recognized to play an important role for the growth of early (z ~ 7) super-massive black holes. While progresses have been made in understanding their formation and growth, their observational signatures remain largely unexplored. As a result, no detection of such sources has been confirmed so far. Supported by numerical simulations, we present a novel photometric method to identify black hole seed candidates in deep multi-wavelength surveys. We predict that these highly-obscured sources are characterized by a s…
We investigate the environment in which direct-collapse black holes may form by analysing a cosmological, hydrodynamical simulation that is part of the First Billion Years project. This simulation includes the most relevant physical processes leading to direct collapse of haloes, most importantly, molecular hydrogen depletion by dissociation of $H_2$ and $H^-$ from the evolving Lyman-Werner radiation field. We selected a sample of pristine atomic cooling haloes that have never formed stars in their past, have not been polluted with heavy elements and are cooling predominantly via atomic hydrog…
A perfect irrotational fluid with the equation of state of dust, Irrotational Dark Matter (IDM), is incapable of virializing and instead forms a cosmoskeleton of filaments with supermassive black holes at the joints. This stark difference from the standard cold dark matter (CDM) scenario arises because IDM must exhibit potential flow at all times, preventing shell-crossing from occurring. This scenario is applicable to general non-oscillating scalar-field theories with a small sound speed. Our model of combined IDM and CDM components thereby provides a solution to the problem of forming the ob…
The nature of the seeds of the observed high-z super-massive black holes (SMBH) is unknown. Although different options have been proposed, involving e.g. intermediate mass direct collapse black holes, BH remnants of massive stars remain the most natural explanation. To identify the most favorable conditions (if any) for their rapid growth, we study the accretion rate of a M_BH = 100M_sun BH formed in a typical z = 10 galaxy under different conditions (e.g. galaxy structure, BH initial position and velocity). We model the galaxy baryonic content and follow the BH orbit and accretion history for…
We report the discovery of a luminous quasar, J1007+2115 at $z=7.515$ ("Pōniuā'ena"), from our wide-field reionization-era quasar survey. J1007+2115 is the second quasar now known at $z>7.5$, deep into the reionization epoch. The quasar is powered by a $(1.5\pm0.2)\times10^9$ $M_{\odot}$ supermassive black hole (SMBH), based on its broad MgII emission-line profile from Gemini and Keck near-IR spectroscopy. The SMBH in J1007+2115 is twice as massive as that in quasar J1342+0928 at $z=7.54$, the current quasar redshift record holder. The existence of such a massive SMBH just 700 million years af…
The existence of $10^9\ {\rm M_\odot}$ supermassive black holes (SMBHs) within the first billion years of the universe remains a puzzle in our conventional understanding of black hole formation and growth. Several suggested formation pathways for these SMBHs lead to a heavy seed, with an initial black hole mass of $10^4-10^6~{\rm M_\odot}$. This can lead to an overly massive BH galaxy (OMBG), whose nuclear black hole's mass is comparable to or even greater than the surrounding stellar mass: the black hole to stellar mass ratio is $M_{\rm bh}/M_* \gg 10^{-3}$, well in excess of the typical valu…
Magnetic fields play a pivotal role in the physics of interstellar medium in galaxies, but there are few observational constraints on how they evolve across cosmic time. Spatially resolved synchrotron polarization maps at radio wavelengths reveal well-ordered large-scale magnetic fields in nearby galaxies that are believed to grow from a seed field via a dynamo effect. To directly test and characterize this theory requires magnetic field strength and geometry measurements in cosmologically distant galaxies, which are challenging to obtain due to the limited sensitivity and angular resolution o…
Observations of high-redshift quasars indicate that super massive black holes (SMBHs) with masses greater than ${\sim}10^9~M_\odot$ were assembled within the first billion years after the Big Bang. It is unclear how such massive black holes formed so early. One possible explanation is that these SMBHs were seeded by `heavy' direct collapse black holes (DCBHs) with masses of $M_{\rm BH}\approx10^5~M_\odot$, but observations have not yet confirmed or refuted this scenario. In this Letter, we utilize a cosmological N-body simulation to demonstrate that before they grow roughly an order of magnitu…
Understanding the growth of high redshift massive black holes (MBHs) is a problem of great astrophysical interest. The most luminous quasars at $z>6$ are frequently observed but they represent only the tip of the iceberg as the majority of the low luminosity AGN population remains undetected. In the present study, we perform a radiation hydrodynamics cosmological simulation to study the growth of "normal" black holes in the high redshift universe. In our simulation we model the formation of Pop III and Pop II stars along with their chemical, mechanical and radiative feedback. We consider both …
The rapid assembly of the massive black holes that power the luminous quasars observed at $z \sim 6-7$ remains a puzzle. Various direct collapse models have been proposed to head-start black hole growth from initial seeds with masses $\sim 10^5\,\rm M_\odot$, which can then reach a billion solar mass while accreting at the Eddington limit. Here we propose an alternative scenario based on radiatively inefficient super-critical accretion of stellar-mass holes embedded in the gaseous circum-nuclear discs (CNDs) expected to exist in the cores of high redshift galaxies. Our sub-pc resolution hydrod…
Massive Black Holes Seeded by Dark Matter -- Implications for Little Red Dots and Gravitational Wave Signatures
John A. Paulson School of Engineering and Applied Sciences, Harvard University（哈佛大学约翰·A·保尔森工程与应用科学学院）；Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology（麻省理工学院卡弗里天体物理与空间研究所）；Theory Division, Fermilab（费米实验室理论部）；Kavli Institute for Cosmological Physics, University of Chicago（芝加哥大学卡弗里宇宙物理学研究所）；Kavli Institute for Astronomy and Astrophysics, Peking University（北京大学卡弗里天文学与天体物理研究所）
