We investigate the Hoyle-Lyttleton accretion of dusty-gas for the case where the central source is the black hole accretion disk. By solving the equation of motion taking into account the radiation force which is attenuated by the dust absorption, we reveal the steady structure of the flow around the central object. We find that the mass accretion rate tends to increase with an increase of the optical thickness of the flow and the gas can accrete even if the disk luminosity exceeds the Eddington luminosity for the dusty-gas, since the radiation force is weakened by the attenuation via the dust absorption. When the gas flows in from the direction of the rotation axis for the disk with $Γ^{'}=3.0$, the accretion rate is about 93% of the Hoyle-Lyttleton accretion rate if $τ_{\rm{HL}}=3.3$ and zero for $τ_{\rm{HL}}=1.0$, where $Γ^{'}$ is the Eddington ratio for the dusty-gas and $τ_{\rm{HL}}$ is the typical optical thickness of the Hoyle-Lyttleton radius. Since the radiation flux in the direction of disk plane is small, the radiation force tends not to prevent gas accretion from the direction near the disk plane. For $τ_{\rm{HL}}=3.3$ and $Γ^{'}=3.4$, although the accretion is impossible in the case of $Θ=0$, the accretion rate is 28% of the Hoyle-Lyttleton one in the case of $Θ=90$, where $Θ$ is the angle between the direction the gas is coming from and the rotation axis of the disk. We also obtain relatively high accretion luminosity that is realized when the accretion rate of the disk onto the BH is consistent with that via the Hoyle-Lyttleton mechanism taking into account the effect of radiation. This implies the intermediate-mass black holes moving in the dense dusty-gas are identified as luminous objects in the infrared band.
An isolated star moving supersonically through a uniform gas accretes material from its gravitationally-induced wake. The rate of accretion is set by the accretion radius of the star and is well-described by classical Bondi-Hoyle-Lyttleton theory. Stars, however, are not born in isolation. They form in clusters where they accrete material that is influenced by all the stars in the cluster. We perform three-dimensional hydrodynamic simulations of clusters of individual accretors embedded in a uniform-density wind in order to study how the accretion rates experienced by individual cluster member…
Binary stars often move through an ambient medium from which they accrete material and angular momentum, as in triple-star systems, star-forming clouds, young globular clusters and in the centres of galaxies. A binary form of Bondi-Hoyle-Lyttleton accretion results whereby the accretion rate depends on the binary properties: the stellar masses and separation, and the relative wind speed. We present the results of simulations performed with the hydrodynamic code GANDALF, to determine the mass accretion rates over a range of binary separations, inclinations and mass ratios. When the binary separ…
Three-dimensional radiation hydrodynamics simulations of wandering intermediate-mass black holes considering the anisotropic radiation and dust sublimation
Several processes may limit the accretion rate onto a super-massive black hole (SMBH). Two processes that are commonly considered (e.g., for sub-grid prescriptions) are Bondi-Hoyle-Lyttleton accretion and the Eddington limit. A third one is AGN wind feedback. It has been long suggested that such a wind feedback regulates the final SMBH mass, however, it has been shown recently that AGN winds can also regulate the average accretion rate at a level consistent with observations of high redshift AGNs. In this paper we study the effect of wind feedback on the accretion rate using 2D, high resolutio…
Using two-dimensional magnetohydrodynamic simulations, we investigated the gas dynamics around a black hole plunging into a molecular cloud. In these calculations, we assumed a parallel-magnetic-field layer in the cloud. The size of the accelerated region is far larger than the Bondi-Hoyle-Lyttleton radius, being approximately inversely proportional to the Alfvén Mach number for the plunging black hole. Our results successfully reproduce the "Y" shape in position velocity maps of the "Bullet" in the W44 molecular cloud. The size of the Bullet is also reproduced within an order of magnitude usi…
We study accretion environments of active galactic nuclei when a super-massive black hole wanders in a circum-nuclear region and passes through an interstellar medium there. It is expected that a Bondi-Hoyle-Lyttleton type accretion of the interstellar matter takes place and an accretion stream of matter trapped by the black hole gravitational field appears from a tail shock region. Since the trapped matter is likely to have a certain amount of specific angular momentum, the accretion stream eventually forms an accretion ring around the black hole. According to the recent study, the accretion …
We present post-Newtonian $N$-body simulations on mergers of accreting stellar-mass black holes (BHs), where such general relativistic effects as the pericenter shift and gravitational wave (GW) emission are taken into consideration. The attention is concentrated on the effects of the dynamical friction and the Hoyle-Lyttleton mass accretion by ambient gas. We consider a system composed of ten BHs with initial mass of $30~M_\odot$. As a result, we show that mergers of accreting stellar-mass BHs are classified into four types: a gas drag-driven, an interplay-driven, a three body-driven, or an a…
Galaxies and massive black holes (BHs) presumably grow via galactic merging events and subsequent BH coalescence. As a case study, we investigate the merging event between the Andromeda galaxy (M31) and a satellite galaxy. We compute the expected observational appearance of the massive BH that was at the center of the satellite galaxy prior to the merger, and is currently wandering in the M31 halo. We demonstrate that a radiatively inefficient accretion flow with a bolometric luminosity of a few tens of solar luminosities develops when Hoyle-Lyttleton accretion onto the BH is assumed. We compu…
Whilst in galaxy-size simulations, supermassive black holes (SMBH) are entirely handled by sub-grid algorithms, computational power now allows the accretion radius of such objects to be resolved in smaller scale simulations. In this paper, we investigate the impact of resolution on two commonly used SMBH sub-grid algorithms; the Bondi-Hoyle-Lyttleton (BHL) formula for accretion onto a point mass, and the related estimate of the drag force exerted onto a point mass by a gaseous medium. We find that when the accretion region around the black hole scales with resolution, and the BHL formula is ev…
Understanding the formation and growth of supermassive black holes (SMBHs) at high redshift represents a major challenge for theoretical models. In this work we investigate the early evolution of the first SMBHs by constraining their distribution in mass and luminosity at $z > 4$. In particular, we focus on the poorly explored low-mass end of the nuclear black hole (BH) distribution down to $z \simeq 4$, and explore its connection with the nature of the first BH seeds and the processes governing their mass growth. To this aim, we have developed CAT (Cosmic Archaeology Tool), a new semi-analyti…
Active galactic nucleus (AGN) feedback from accreting supermassive black holes (SMBHs) is an essential ingredient of galaxy formation simulations. The orbital evolution of SMBHs is affected by dynamical friction that cannot be predicted self-consistently by contemporary simulations of galaxy formation in representative volumes. Instead, such simulations typically use a simple "repositioning" of SMBHs, but the effects of this approach on SMBH and galaxy properties have not yet been investigated systematically. Based on a suite of smoothed particle hydrodynamics simulations with the SWIFT code a…
More than two hundred supermassive black holes (SMBHs) of masses $\gtrsim 10^9\,\mathrm{M_{\odot}}$ have been discovered at $z \gtrsim 6$. One promising pathway for the formation of SMBHs is through the collapse of supermassive stars (SMSs) with masses $\sim 10^{3-5}\,\mathrm{M_{\odot}}$ into seed black holes which could grow upto few times $10^9\,\mathrm{M_{\odot}}$ SMBHs observed at $z\sim 7$. In this paper, we explore how SMSs with masses $\sim 10^{3-5}\,\mathrm{M_{\odot}}$ could be formed via gas accretion and runaway stellar collisions in high-redshift, metal-poor nuclear star clusters (N…
We introduce a new model for the accretion and feedback of supermassive black hole (SMBH) binaries to the KETJU code, which enables us to resolve the evolution of SMBH binaries down to separations of tens of Schwarzschild radii in gas-rich galaxy mergers. Our subgrid binary accretion model extends the widely used Bondi--Hoyle--Lyttleton accretion into the binary phase and incorporates preferential mass accretion onto the secondary SMBH, which is motivated by results from small-scale hydrodynamical circumbinary disc simulations. We perform idealised gas-rich disc galaxy merger simulations using…
We have mapped 12CO J=3-2 and other molecular lines from the "water-fountain" bipolar pre-planetary nebula (PPN) IRAS 16342-3814 with ~0."35 resolution using ALMA. We find (i) two very high-speed knotty, jet-like molecular outflows, (ii) a central high-density (> few x 10^6 cm^{-3}), expanding torus of diameter 1300 AU, and (iii) the circumstellar envelope of the progenitor AGB, generated by a sudden, very large increase in the mass-loss rate to >3.5 x 10^{-4} Msun/yr in the past ~455 yr. Strong continuum emission at 0.89 mm from a central source (690 mJy), if due to thermally-emitting dust, i…
During galaxy mergers the gas falls to the center, triggers star formation, and feeds the rapid growth of supermassive black holes (SMBHs). SMBHs respond to this fueling by supplying energy back to the ambient gas. Numerical studies suggest that this feedback is necessary to explain why the properties of SMBHs and the formation of bulges are closely related. This intimate link between the SMBH's mass and the large scale dynamics and luminosity of the host has proven to be a difficult issue to tackle with simulations due to the inability to resolve all the relevant length scales simultaneously.…
We study the orbital evolution and accretion history of massive black hole (MBH) pairs in rotationally supported circumnuclear discs up to the point where MBHs form binary systems. Our simulations have high resolution in mass and space which, for the first time, makes it feasible to follow the orbital decay of a MBH either counter- or co-rotating with respect to the circumnuclear disc. We show that a moving MBH on an initially counter-rotating orbit experiences an "orbital angular momentum flip" due to the gas-dynamical friction, i.e., it starts to corotate with the disc before a MBH binary fo…
