We perform two-dimensional radiation hydrodynamical simulations of accretion flows onto black holes (BHs) at the nuclei of protogalaxies, and study the impact of mechanical and radiative feedback on rapid growth of BHs. The outflows deposit mass, momentum and energy into the surrounding medium and prevent mass accretion onto the BH, resulting in the reduction of radiative output. We find that when the BH is embedded in a dense gas core, ionizing radiation attenuated by inefficient BH feeding owing to mechanical feedback hardly affects the gas dynamics at the BH gravitational sphere of influence, from which intense inflows of neutral gas occur at rates substantially exceeding the Eddington limit without impeded by photoionization and heating. Since mechanical power of outflows driven by the rapidly accreting BH is sufficiently strong, bipolar outflows completely evacuate the surrounding gas in the polar region but mass inflows through the equatorial region maintain the BH accretion rate as high as $\sim 300-10^3~\dot{M}_{\rm Edd}$, which is reduced by one order of magnitude from those with radiative feedback alone. Furthermore, we find that the critical gas density required for rapid accretion is lower by a factor of $\sim 3$ nearly independently of BH mass, when mechanical feedback is considered. By studying the dependence on outflow model parameters (e.g., opening angle, mass-loading degree into outflows, velocity), we conclude that contrary to naive expectation, the existence of stronger outflow leads to the transition to rapid accretion phases more efficiently. Rapidly growing BHs inject mechanical power with $\sim 0.1-1\%$ of the radiative luminosity into their host galaxy scales, which is used for cosmological simulations.
We show that black holes supplied with mass at hyper--Eddington rates drive outflows with mildly sub--relativistic velocities. These are $\sim 0.1 - 0.2c$ for Eddington accretion factors $\dot m_{\rm acc} \sim 10 - 100$, and $\sim 1500\,{\rm km\, s^{-1}}$ for $\dot m_{\rm acc} \sim 10^4$. Winds like this are seen in the X--ray spectra of ultraluminous sources (ULXs), strongly supporting the view that ULXs are stellar--mass compact binaries in hyper--Eddington accretion states. SS433 appears to be an extreme ULX system ($\dot m_{\rm acc} \sim 10^4$) viewed from outside the main X--ray emission …
By performing three-dimensional hydrodynamical simulations of a galaxy in an isolated dark matter halo, we follow the evolution of the spin parameter $a$ of a black hole (BH) undergoing super-Eddington phases throughout its growth. This regime, suspected to be accompanied by powerful jet outflows, is expected to decrease the BH spin magnitude. We combine super-Eddington accretion with sub-Eddington phases (quasar and radio modes) and follow the BH spin evolution. Due to the low frequency of super-Eddington episodes, relativistic jets in this regime are not able to decrease the magnitude of the…
We perform two-dimensional radiation hydrodynamical simulations of accretion flows onto a black hole (BH) with a mass of $10^3\leq M_{\rm BH}/M_{\odot} \lesssim 10^6$ in order to study rapid growth of BHs in the early Universe. For spherically symmetric flows, hyper-Eddington accretion onto the BH from outside the Bondi radius can occur unimpeded by radiation feedback only when the BH mass is higher than $\simeq 10^4~M_{\odot}(n_\infty/10^5~{\rm cm}^{-3})^{-1}(T_\infty/10^4~{\rm K})^{3/2}$, where $n_\infty$ and $T_\infty$ are the density and temperature of ambient gas. Here, we study the prope…
Super-Eddington accretion is one scenario that may explain the rapid assembly of $\sim 10^9\rm\, M_\odot$ supermassive black holes (BHs) within the first billion year of the Universe. This critical regime is associated with radiatively inefficient accretion and accompanied by powerful outflows in the form of winds and jets. By means of hydrodynamical simulations of BH evolution in an isolated galaxy and its host halo with 12 pc resolution, we investigate how super-Eddington feedback affects the mass growth of the BH. It is shown that super-Eddington feedback efficiently prevents BH growth with…
The physical properties of the accretion flow and of the X-ray emitting plasma, in supermassive black holes accreting at extreme Eddington rates, are still very unclear. Here we present the analysis of simultaneous XMM-Newton and NuSTAR observations of the hyper-Eddington Seyfert 1 galaxy IRAS 04416+1215, carried out in 2020. The main goal of these observations is to investigate the properties of the X-ray corona, as well as the structure of the accretion flow and of the circumnuclear environment, in this regime of extreme accretion. IRAS 04416+1215 has one of the highest Eddington ratio ($λ_{…
We perform one-dimensional radiation hydrodynamical simulations to solve accretion flows onto massive black holes (BHs) with a very high rate. Assuming that photon trapping limits the luminosity emerging from the central region to $L\lesssim L_{\rm Edd}$, Inayoshi, Haiman & Ostriker (2016) have shown that an accretion flow settles to a "hyper-Eddington" solution, with a steady and isothermal ($T\simeq 8000$ K) Bondi profile reaching $\gtrsim 5000$ times the Eddington accretion rate $\dot{M}_{\rm Edd}\equiv L_{\rm Edd}/c^2$. Here we address the possibility that gas accreting with finite angular…
Little Red Dots as Supermassive Counterparts of SS 433: A Hyper-Eddington Accretion Framework
Xiamen University（厦门大学）；University of Cambridge（剑桥大学）；Shanghai Astronomical Observatory, Chinese Academy of Sciences（中国科学院上海天文台）；Peking University（北京大学）；University College London（伦敦大学学院）；University of Science and Technology of China（中国科学技术大学）
We study very-high rate spherically symmetric accretion flows onto a massive black hole (BH; 10^2 < M_BH < 10^6 Msun) embedded in a dense gas cloud with a low abundance of metals, performing one-dimensional hydrodynamical simulations which include multi-frequency radiation transfer and non-equilibrium primordial chemistry. We find that rapid gas supply from the Bondi radius at a hyper-Eddington rate can occur without being impeded by radiation feedback when (n/10^5 cm^-3) > (M_BH/10^4Msun)^{-1}(T/10^4 K)^{3/2}, where n and T are the density and temperature of ambient gas outside of the Bondi r…
The rate at which matter flows into a galactic nucleus during early phases of galaxy evolution can sometimes exceed the Eddington limit of the growing central black hole by several orders of magnitude. We discuss the necessary conditions for the black hole to actually accrete this matter at such a high rate, and consider the observational appearance and detectability of a hyperaccreting black hole. In order to be accreted at a hyper-Eddington rate, the infalling gas must have a sufficiently low angular momentum. Although most of the gas is accreted, a significant fraction accumulates in an opt…
We present simulated optical light curves of super-Eddington tidal disruption events (TDEs) using the zero-Bernoulli accretion (ZEBRA) flow model, which proposes that during the super-Eddington phase, the disc is quasi-spherical, radiation-pressure dominated, and accompanied by the production of strong jets. We construct light curves for both on- and off-axis (with respect to the jet) observers to account for the anisotropic nature of the jetted emission. We find that at optical wavelengths, emission from the accretion flow is orders of magnitude brighter than that produced by the jet, even wi…
Accretion at super-Eddington rates is expected to be accompanied by strong outflows. Such outflows are observed in Galactic X-ray binaries and extragalactic Ultra-luminous X-ray sources (ULXs). However, due to their large source distances, ULX outflows are challenging to detect and study in detail. Galactic neutron stars accreting from a Be-star companion at super-Eddington rates show many similarities to ULX pulsars, and therefore offer an alternative approach to study outflows in this accretion regime. Here, we present Chandra high-resolution spectroscopy of such a super-Eddington accreting …
After the destruction of the star during a tidal disruption event (TDE), the cataclysmic encounter between a star and the supermassive black hole (SMBH) of a galaxy, approximately half of the original stellar debris falls back onto the hole at a rate that can initially exceed the Eddington limit by orders of magnitude. We argue that the angular momentum of this matter is too low to allow it to attain a disk-like configuration with accretion proceeding at a mildly super-Eddington rate, the excess energy being carried away by a combination of radiative losses and radially distributed winds. Inst…
Recent simulations on super-Eddington accretion flows have shown that, apart from the diffusion process, the vertical advection based on magnetic buoyancy can be a more efficient process to release the trapped photons in the optically thick disk. As a consequence, the radiative luminosity from the accretion disk can be far beyond the Eddington value. Following this spirit, we revisit the structure and radiation of hyper-accretion disks with mass accretion rates in the range $10^{-3}\sim 10~M_{\sun}~{\rm s}^{-1}$. Our results show that, due to the strong cooling through the vertical advection, …
X-ray continuum spectra of super-Eddington accretion flow are studied by means of Monte Carlo radiative transfer simulations based on the radiation hydrodynamic simulation data, in which both of thermal and bulk Compton scatterings are taken into account. We compare the calculated spectra of accretion flow around black holes with masses of $M_{\rm BH} = 10, 10^2, 10^3$, and $10^4 M_\odot$ for a fixed mass injection rate (from the computational boundary at $10^3 r_{\rm s}$) of $10^3 L_{\rm Edd}/c^2$ (with $r_{\rm s}$, $L_{\rm Edd}$, and $c$ being the Schwarzschild radius, the Eddington luminosi…
The measurement of the period and period derivative, and the canonical model of dipole radiation have provided a method to estimate the low superficial magnetic fields in the so-called Central Compact Objects (CCOs). In the present work, a scenario is introduced in order to explain the magnetic behavior of such CCOs. Based on magnetohydrodynamic simulations of the post core-collapse supernova phase during the hypercritical accretion episode, we argue that the magnetic field of a newborn neutron star could have been early buried. During this phase, thermal neutrinos are created mainly by the pa…
ALMA High-J CO Spectroscopy of High-Redshift Galaxies. II. 0.03" Resolution CO Kinematics Reveal Super-Eddington Accretion in a Dust-Obscured Galaxy at z=3.111
Faculty of Engineering, Hokkai-Gakuen University（北海道学园大学工学部）
When a black hole accretes close to the Eddington limit, the astrophysical jet is often accompanied by radiatively driven, wide-aperture and mildly relativistic winds. Powerful winds can produce significant non-thermal radio emission via shocks. Among the nearby critical accretion quasars, PDS 456 has a very massive black hole (about one billion solar masses), shows a significant star-forming activity (about seventy solar masses per year) and hosts exceptionally energetic X-ray winds (power up to twenty per cent of the Eddington luminosity). To probe the radio activity in this extreme accretio…
Compact objects are expected to exist in the accretion disks of supermassive black holes (SMBHs) in active galactic nuclei (AGNs), and in the presence of such a dense environment ($\sim 10^{14}\,{\rm cm^{-3}}$), they will form a new kind of stellar population denoted as Accretion-Modified Stars (AMSs). This hypothesis is supported by recent LIGO/Virgo detection of the mergers of very high-mass stellar binary black holes (BHs). We show that the TZOs will be trapped by the SMBH-disk within a typical AGN lifetime. In the context of SMBH-disks, the rates of Bondi accretion onto BHs are $\sim 10^{9…
We investigate the X-ray spectrum, variability and the surrounding ionized bubble of NGC1313 X-2 to explore the physics of super-Eddington accretion. Beyond the Eddington luminosity, the accretion disk of NGC1313 X-2 is truncated at a large radius ($\sim$ 50 times of innermost stable circular orbit), and displays the similar evolution track with both luminous Galactic black-hole and neutron star X-ray binaries. In super-critical accretion, the speed of radiatively driven outflows from the inner disk is mildly relativistic. Such ultra-fast outflows would be over ionized and might produce weak F…
The recent advanced LIGO/Virgo detections of gravitational waves (GWs) from stellar binary black hole (BBH) mergers, in particular GW190521, which is potentially associated with a quasar, have stimulated renewed interest in active galactic nuclei (AGNs) as factories of merging BBHs. Compact objects evolving from massive stars are unavoidably enshrouded by a massive envelope to form accretion-modified stars (AMSs) in the dense gaseous environment of a supermassive black hole (SMBH) accretion disk. We show that most AMSs form binaries due to gravitational interaction with each other during radia…
The Laser Interferometer Gravitational-Wave Observatory, LIGO, found direct evidence for double black hole binaries emitting gravitational waves. Galactic nuclei are expected to harbor the densest population of stellar-mass black holes. A significant fraction ($\sim30\%$) of these black holes can reside in binaries. We examine the fate of the black hole binaries in active galactic nuclei, which get trapped in the inner region of the accretion disk around the central supermassive black hole. We show that binary black holes can migrate into and then rapidly merge within the disk well within a Sa…
A bright flare from a galactic nucleus followed at late times by a $t^{-5/3}$ decay in luminosity is often considered the signature of the complete tidal disruption of a star by a massive black hole. The flare and power-law decay are produced when the stream of bound debris returns to the black hole, self-intersects, and eventually forms an accretion disk or torus. In the canonical scenario of a solar-type star disrupted by a $10^{6}\; M_\odot$ black hole, the time between the disruption of the star and the formation of the accretion torus could be years. We present fully general relativistic …
Ultraluminous X-ray sources (ULXs) are bright extragalactic sources with X-ray luminosities above 10^39 erg/s powered by accretion onto compact objects. According to the first studies performed with XMM-Newton ULXs seemed to be excellent candidates to host intermediate-mass black holes (10^2-4 solar masses). However, in the last years the interpretation of super-Eddington accretion onto stellar-mass black holes or neutron stars for most ULXs has gained a strong consensus. One critical missing piece to confirm the super-Eddington scenario was the direct detection of the massive, radiatively-dri…
Newborn black holes in collapsing massive stars can be accompanied by a fallback disk. The accretion rate is typically super-Eddington and strong disk outflows are expected. Such outflows could be directly observed in some failed explosions of compact (blue supergiants or Wolf-Rayet stars) progenitors, and may be more common than long-duration gamma-ray bursts. Using an analytical model, we show that the fallback disk outflows produce blue UV-optical transients with a peak bolometric luminosity of ~10^(42-43) erg s^-1 (peak R-band absolute AB magnitudes of -16 to -18) and an emission duration …
The formation of supermassive black holes is still an outstanding question. In the quasi-star scenario, black hole seeds experience an initial super-Eddington growth, that in less than a million years may leave a $10^4-10^5$ M$_{\odot}$ black hole at the centre of a protogalaxy at $z \sim 20-10$. Super-Eddington accretion, however, may be accompanied by vigorous mass loss that can limit the amount of mass that reaches the black hole. In this paper, we critically assess the impact of radiative driven winds, launched from the surface of the massive envelopes from which the black hole accretes. S…
The hyper luminous X-ray source HLX-1 in the galaxy ESO 243-49, currently the best intermediate mass black hole candidate, displays spectral transitions similar to those observed in Galactic black hole binaries, but with a luminosity 100-1000 times higher. We investigated the X-ray properties of this unique source fitting multi-epoch data collected by Swift, XMM-Newton & Chandra with a disk model computing spectra for a wide range of sub- and super-Eddington accretion rates assuming a non-spinning black hole and a face-on disk (i = 0 deg). Under these assumptions we find that the black hole in…
We reformulate the adiabatic inflow-outflow (ADIOS) model for radiatively inefficient accretion flows, treating the inflow and outflow zones on an equal footing. For purely adiabatic flows (i.e., with no radiative losses), we show that the mass flux in each zone must satisfy Mdot ~ R^n with n=1, in contrast to previous work in which 0<n< 1 is a free parameter but in rough agreement with numerical simulations. We also demonstrate that the resulting two-zone ADIOS models are not dynamically self-consistent without the introduction of an energy source close in to the central regions of the flow; …
The small subset of hyper-luminous X-ray sources with luminosities in excess of ~1E41 erg/s are hard to explain without the presence of an intermediate mass black hole, as significantly super-Eddington accretion and/or very small beaming angles are required. The recent discovery of HLX-1, the most luminous object in this class with a record breaking luminosity of ~1E42 erg/s in the galaxy ESO 243-49, therefore currently provides some of the strongest evidence for the existence of intermediate mass black holes. HLX-1 is almost an order of magnitude brighter than the other hyper-luminous sources…
We consider radio emission from a newborn black hole (BH), which is accompanied by a mini-disk with a mass of $\lesssim M_\odot$. Such a disk can be formed from an outer edge of the progenitor's envelope, especially for metal-poor massive stars and/or massive stars in close binaries. The disk accretion rate is typically super-Eddington and an ultrafast outflow with a velocity of $\sim 0.1\mbox{-}0.3\,c$ will be launched into the circumstellar medium. The outflow forms a collisionless shock, and electrons are accelerated and emit synchrotron emission in radio bands with a flux of $\sim 10^{26-3…
We present the results from an X-ray and optical study of a new sample of eight extreme luminosity ultraluminous X-ray source (ULX) candidates, which were selected as the brightest ULXs (with L_X > 5x10^40 erg/s) located within 100 Mpc identified in a cross correlation of the 2XMM-DR1 and RC3 catalogues. These objects are so luminous that they are difficult to describe with current models of super-Eddington accretion onto all but the most massive stellar remnants; hence they are amongst the most plausible candidates to host larger, intermediate-mass black holes (IMBHs). Two objects are luminou…
Hyperaccretion flows with mass accretion rates far above the Eddington rate have an N-shaped equilibrium curve on the $Σ$-$\dot{M}$ plane (with $Σ$ and $\dot{M}$ being surface density and mass accretion rate, respectively). The accretion flow on the lower $Σ$ branch of the N-shape is optically thick, advection-dominated accretion flow (ADAF) while that on the upper one is neutrino-dominated accretion flow (NDAF). The middle branch has a negative slope on the $Σ$-$\dot{M}$ plane, meaning that the flow on this branch is secularly unstable. To investigate how the instability affects the flow stru…
Stellar evolution theory predicts a "gap" in the black hole birth function caused by the pair instability. Presupernova stars that have a core mass below some limiting value, Mlo, after all pulsational activity is finished, collapse to black holes, whereas more massive ones, up to some limiting value, Mhi, explode, promptly and completely, as pair-instability supernovae. Previous work has suggested Mlo is approximately 50 solar masses and Mhi is approximately 130 solar masses. These calculations have been challenged by recent LIGO observations that show many black holes merging with individual…
Both types of long and short gamma ray bursts involve a stage of a hyper-Eddington accretion of hot and dense plasma torus onto a newly born black hole. The prompt gamma ray emission originates in jets at some distance from this 'central engine' and in most events is rapidly variable, having a form of spikes and subpulses. This indicates at the variable nature of the engine itself, for which a plausible mechanism is an internal instability in the accreting flow. We solve numerically the structure and evolution of the neutrino-cooled torus. We take into account the detailed treatment of the mic…
The origin of iPTF14hls, which had Type IIP supernova-like spectra but kept bright for almost two years with little spectral evolution, is still unclear. We here propose that iPTF14hls was not a sudden outburst like supernovae but rather a long-term outflow similar to stellar winds. The properties of iPTF14hls, which are at odds with a supernova scenario, become natural when interpreted as a stellar wind with variable mass-loss rate. Based on the wind hypothesis, we estimate the mass-loss rates of iPTF14hls in the bright phase. We find that the instantaneous mass-loss rate of iPTF14hls during …
