Abstract
The dynamics of black hole (BH) seeds in high-redshift galaxies is key to understand their ability to grow via accretion and to pair in close binaries during galactic mergers. To properly ...follow the dynamics of BHs we develop a physically motivated model to capture unresolved dynamical friction from stars, dark matter, and gas. We first validate the model and then we use it to investigate the dynamics of seed BHs born at z ∼ 9 in dwarf proto-galaxies. We perform a suite of zoom cosmological simulations with spatial resolution as high as 10 pc and with a stellar and dark matter mass resolution of $2\times 10^3 \, \, $ and $2\times 10^5 \, \, \mathrm{ M}_{\odot }$, respectively. We first explore the dynamics of a seed BH in the galaxy where it is born and show that it is highly erratic if the seed mass is less than $10^5\, \, \mathrm{ M}_{\odot }$. The dynamics is dominated by the stellar component, whose distribution is irregular and patchy, thus inducing stochasticity in the orbits: the BH may be anywhere in the proto-galaxy. When this dwarf merges into a larger galaxy, it is paramount to simulate the process with very high spatial and mass resolution in order to correctly account for the stripping of the stellar envelope of the satellite BH. The outcome of the encounter could be either a tight binary or, at least temporary, a wandering BH, leading to multiple BHs in a galaxy, each inherited from a different merger.
We develop a subgrid model for the growth of supermassive black holes (BHs) and their associated active galactic nucleus (AGN) feedback in hydrodynamical cosmological simulations. This model ...transposes previous attempts to describe BH accretion and AGN feedback with the smoothed particle hydrodynamics (SPH) technique to the adaptive mesh refinement framework. It also furthers their development by implementing a new jet-like outflow treatment of the AGN feedback which we combine with the heating mode traditionally used in the SPH approach. Thus, our approach allows one to test the robustness of the conclusions derived from simulating the impact of self-regulated AGN feedback on galaxy formation vis-à-vis the numerical method. Assuming that BHs are created in the early stages of galaxy formation, they grow by mergers and accretion of gas at a Eddington-limited Bondi accretion rate. However this growth is regulated by AGN feedback which we model using two different modes: a quasar-heating mode when accretion rates on to the BHs are comparable to the Eddington rate, and a radio-jet mode at lower accretion rates which not only deposits energy, but also deposits mass and momentum on the grid. In other words, our feedback model deposits energy as a succession of thermal bursts and jet outflows depending on the properties of the gas surrounding the BHs. We assess the plausibility of such a model by comparing our results to observational measurements of the co-evolution of BHs and their host galaxy properties, and check their robustness with respect to numerical resolution. We show that AGN feedback must be a crucial physical ingredient for the formation of massive galaxies as it appears to be able to efficiently prevent the accumulation of and/or expel cold gas out of haloes/galaxies and significantly suppress star formation. Our model predicts that the relationship between BHs and their host galaxy mass evolves as a function of redshift, because of the vigorous accretion of cold material in the early Universe that drives Eddington-limited accretion on to BHs. Quasar activity is also enhanced at high redshift. However, as structures grow in mass and lose their cold material through star formation and efficient BH feedback ejection, the AGN activity in the low-redshift Universe becomes more and more dominated by the radio mode, which powers jets through the hot circumgalactic medium.
Supermassive black holes (BHs) at the centres of galaxies can rapidly change their mass and spin by gas accretion and mergers. Using hydrodynamical cosmological simulations, with prescriptions for BH ...growth and feedback from active galactic nuclei, we study how the evolution of BH mass growth is driven by gas accretion and mergers. Using a semi-analytical approach to evolve spins, we also highlight the mechanisms responsible for driving the magnitude and the direction of spins as a function of cosmic time. We find that in the high-redshift universe galaxies maintain large values of gas accretion on to BHs, which therefore is the main driver of their mass and spin evolution. Sustained accretion of cold gas at high redshift tends to align BH spins with the angular momentum of the surrounding gas and maximize their magnitude. Conversely, at low redshift, as BHs get more massive and galaxies more gas poor, the contribution from binary coalescences to the total BH mass growth increases, especially at the high-mass end, and tends to decrease the magnitude of spins and change their direction.
Compaction-driven black hole growth Lapiner, Sharon; Dekel, Avishai; Dubois, Yohan
Monthly notices of the Royal Astronomical Society,
07/2021, Letnik:
505, Številka:
1
Journal Article
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ABSTRACT
We study the interplay between galaxy evolution and central black hole (BH) growth using the NewHorizon cosmological simulation. BH growth is slow when the dark-matter halo is below a golden ...mass of $M_{\rm v}\sim 10^{12}\, \rm M_\odot$, and rapid above it. The early suppression is primarily due to gas removal by supernova (SN) feedback in the shallow potential well, predicting that BHs of ${\sim}10^5\, \rm M_\odot$ tend to lie below the linear relation with bulge mass. Rapid BH growth is allowed when the halo is massive enough to lock in the SN ejecta by its deep potential well and its heated circumgalactic medium (CGM). The onset of BH growth between these two zones is triggered by a wet-compaction event, caused, e.g. by mergers or counter-rotating streams. It brings gas that lost angular momentum into the inner-$1\, {\rm kpc}$ ‘blue nugget’ and causes major transitions in the galaxy structural, kinematic, and compositional properties, including the onset of star-formation quenching. The compaction events are confined to the golden mass by the same mechanisms of SN feedback and hot CGM. The onset of BH growth is associated with its sinkage to the centre due to the compaction-driven deepening of the potential well and the associated dynamical friction. The galaxy golden mass is thus imprinted as a threshold for rapid BH growth, allowing the AGN feedback to keep the CGM hot and maintain long-term quenching. AGN feedback is not causing the onset of quenching; they are both caused by a compaction event when the mass is between the SN and hot-CGM zones.
The interplay between cosmic gas accretion on to galaxies and galaxy mergers drives the observed morphological diversity of galaxies. By comparing the state-of-the-art hydrodynamical cosmological ...simulations HORIZON-AGN and HORIZON-NOAGN, we unambiguously identify the critical role of active galactic nuclei (AGN) in setting up the correct galaxy morphology for the massive end of the population. With AGN feedback, typical kinematic and morpho-metric properties of galaxy populations as well as the galaxy-halo mass relation are in much better agreement with observations. Only AGN feedback allows massive galaxies at the centre of groups and clusters to become ellipticals, while without AGN feedback those galaxies reform discs. It is the merger-enhanced AGN activity that is able to freeze the morphological type of the post-merger remnant by durably quenching its quiescent star formation. Hence morphology is shown to be driven not only by mass but also by the nature of cosmic accretion: at constant galaxy mass, ellipticals are galaxies that are mainly assembled through mergers, while discs are preferentially built from the in situ star formation fed by smooth cosmic gas infall.
Astrophysical plasmas are subject to a tight connection between magnetic fields and the diffusion of particles, which leads to an anisotropic transport of energy. Under the fluid assumption, this ...effect can be reduced to an advection-diffusion equation, thereby augmenting the equations of magnetohydrodynamics. We introduce a new method for solving the anisotropic diffusion equation using an implicit finite-volume method with adaptive mesh refinement and adaptive time-stepping in the ramses code. We apply this numerical solver to the diffusion of cosmic ray energy and diffusion of heat carried by electrons, which couple to the ion temperature. We test this new implementation against several numerical experiments and apply it to a simple supernova explosion with a uniform magnetic field.
In order to understand the physical mechanisms at work during the formation of massive early-type galaxies, we performed six zoomed hydrodynamical cosmological simulations of haloes in the mass range ...4.3 × 1012 ≤ M
vir ≤ 8.0 × 1013 M at z = 0, using the Adaptive Mesh Refinement code ramses. These simulations explore the role of active galactic nuclei (AGN), through jets powered by the accretion on to supermassive black holes on the formation of massive elliptical galaxies. In the absence of AGN feedback, large amounts of stars accumulate in the central galaxies to form overly massive, blue, compact and rotation-dominated galaxies. Powerful AGN jets transform the central galaxies into red extended and dispersion-dominated galaxies. This morphological transformation of disc galaxies into elliptical galaxies is driven by the efficient quenching of the in situ star formation due to AGN feedback, which transform these galaxies into systems built up by accretion. For galaxies mainly formed by accretion, the proportion of stars deposited farther away from the centre increases, and galaxies have larger sizes. The accretion is also directly responsible for randomizing the stellar orbits, increasing the amount of dispersion over rotation of stars as a function of time. Finally, we find that our galaxies simulated with AGN feedback better match the observed scaling laws, such as the size-mass, velocity dispersion-mass, Fundamental Plane relations and slope of the total density profiles at z ∼ 0, from dynamical and strong lensing constraints.
ABSTRACT
While low-mass, star-forming galaxies are often considered as the primary driver of reionization, their actual contribution to the cosmic ultraviolet background is still uncertain, mostly ...because the escape fraction of ionizing photons is only poorly constrained. Theoretical studies have shown that efficient supernova feedback is a necessary condition to create paths through which ionizing radiation can escape into the intergalactic medium. We investigate the possibility that accreting supermassive black holes in early dwarf galaxies may provide additional feedback and enhance the leakage of ionizing radiation. We use a series of high-resolution cosmological radiation hydrodynamics simulations where we isolate the different sources of feedback. We find that supernova feedback prevents the growth of the black hole, thus quenching its associated feedback. Even in cases where the black hole can grow, the structure of the interstellar medium is strongly dominated by supernova feedback. We conclude that, in the dwarf galaxy regime, supermassive black holes do not appear to play a significant role in enhancing the escape fraction and in contributing to the early ultraviolet background.
The presence of a dark matter core in the central kiloparsec of many dwarf galaxies has been a long-standing problem in galaxy formation theories based on the standard cold dark matter paradigm. ...Recent simulations, based on smooth particle hydrodynamics and rather strong feedback recipes, have shown that it was indeed possible to form extended dark matter cores using baryonic processes related to a more realistic treatment of the interstellar medium. Using adaptive mesh refinement, together with a new, stronger supernova feedback scheme that we have recently implemented in the ramses code, we show that it is also possible to form a prominent dark matter core within the well-controlled framework of an isolated, initially cuspy, 1010 M dark matter halo. Although our numerical experiment is idealized, it allows a clean and unambiguous identification of the dark matter core formation process. Our dark matter inner profile is well fitted by a pseudo-isothermal profile with a core radius of 800 pc. The core formation mechanism is consistent with the one proposed by Pontzen & Governato. We highlight two key observational predictions of all simulations that find cusp-core transformations: (i) a bursty star formation history with a peak-to-trough ratio of 5 to 10 and a duty cycle comparable to the local dynamical time and (ii) a stellar distribution that is hot with v/σ ∼ 1. We compare the observational properties of our model galaxy with recent measurements of the isolated dwarf Wolf-Lundmark-Mellote (WLM). We show that the spatial and kinematical distribution of stars and H i gas are in striking agreement with observations, supporting the fundamental role played by stellar feedback in shaping both the stellar and dark matter distribution.
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