ABSTRACT Scaling relations between central black hole (BH) mass and host galaxy properties are of fundamental importance to studies of BH and galaxy evolution throughout cosmic time. Here we ...investigate the relationship between BH mass and host galaxy total stellar mass using a sample of 262 broad-line active galactic nuclei (AGNs) in the nearby universe (z < 0.055), as well as 79 galaxies with dynamical BH masses. The vast majority of our AGN sample is constructed using Sloan Digital Sky Survey spectroscopy and searching for Seyfert-like narrow-line ratios and broad H emission. BH masses are estimated using standard virial techniques. We also include a small number of dwarf galaxies with total stellar masses Mstellar 109.5 M and a subsample of the reverberation-mapped AGNs. Total stellar masses of all 341 galaxies are calculated in the most consistent manner feasible using color-dependent mass-to-light ratios. We find a clear correlation between BH mass and total stellar mass for the AGN host galaxies, with MBH ∝ Mstellar, similar to that of early-type galaxies with dynamically detected BHs. However, the relation defined by the AGNs has a normalization that is lower by more than an order of magnitude, with a BH-to-total stellar mass fraction of MBH/Mstellar ∼ 0.025% across the stellar mass range 108 ≤ Mstellar/M ≤ 1012. This result has significant implications for studies at high redshift and cosmological simulations in which stellar bulges cannot be resolved.
ABSTRACT Short-lived intermittent phases of super-critical (super-Eddington) growth, coupled with star formation via positive feedback, may account for early growth of massive black holes (MBH) and ...coevolution with their host spheroids. We estimate the possible growth rates and duty cycles of these episodes, both assuming slim accretion disk solutions and adopting the results of recent numerical simulations. The angular momentum of gas joining the accretion disk determines the length of the accretion episodes and the final mass that an MBH can reach. The latter can be related to the gas velocity dispersion and, in galaxies with low-angular momentum gas, the MBH can reach a higher mass. When the host galaxy is able to sustain inflow rates at 1-100 , replenishing and circulation lead to a sequence of short ( yr), heavily obscured accretion episodes that increase the growth rates, with respect to an Eddington-limited case, by several orders of magnitude. Our model predicts that the ratio of the MBH accretion rate-to-star formation rate is 10−2 or higher, leading, at early epochs, to a ratio of MBH-to-stellar mass that is higher than the "canonical" value of , which is in agreement with current observations. Our model makes specific predictions that long-lived super-critical accretion occurs only in galaxies with copious low-angular momentum gas, and, in this case, the MBH is more massive at a fixed velocity dispersion.
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.
From the first stars to the first black holes Valiante, Rosa; Schneider, Raffaella; Volonteri, Marta ...
Monthly notices of the Royal Astronomical Society,
04/2016, Letnik:
457, Številka:
3
Journal Article
Recenzirano
Odprti dostop
The growth of the first supermassive black holes (SMBHs) at z > 6 is still a major challenge for theoretical models. If it starts from black hole (BH) remnants of Population III stars (light seeds ...with mass ∼100 M⊙), it requires super-Eddington accretion. An alternative route is to start from heavy seeds formed by the direct collapse of gas on to an ∼105 M⊙ BH. Here we investigate the relative role of light and heavy seeds as BH progenitors of the first SMBHs. We use the cosmological, data constrained semi-analytic model gamete/qsodust to simulate several independent merger histories of z > 6 quasars. Using physically motivated prescriptions to form light and heavy seeds in the progenitor galaxies, we find that the formation of a few heavy seeds (between 3 and 30 in our reference model) enables the Eddington-limited growth of SMBHs at z > 6. This conclusion depends sensitively on the interplay between chemical, radiative and mechanical feedback effects, which easily erase the conditions that allow the suppression of gas cooling in the low-metallicity gas (Z < Z
cr and J
LW > J
cr). We find that heavy seeds cannot form if dust cooling triggers gas fragmentation above a critical dust-to-gas mass ratio (
${\cal D} \ge {\cal D}_{\rm cr}$
). In addition, the relative importance of light and heavy seeds depends on the adopted mass range for light seeds, as this dramatically affects the history of cold gas along the merger tree, by both SN- and AGN-driven winds.
ABSTRACT
The presence of massive black holes (BHs) with masses of the order of $10^9\, {\rm M_\odot }$, powering bright quasars when the Universe was less than 1 Gyr old, poses strong constraints on ...their formation mechanism. Several scenarios have been proposed to date to explain massive BH formation, from the low-mass seed BH remnants of the first generation of stars to the massive seed BHs resulting from the rapid collapse of massive gas clouds. However, the plausibility of some of these scenarios to occur within the progenitors of high-z quasars has not yet been thoroughly explored. In this work, we investigate, by combining dark-matter only N-body simulations with a semi-analytic framework, whether the conditions for the formation of massive seed BHs from synchronized atomic-cooling halo pairs and/or dynamically heated (DH) mini-haloes are fulfilled in the overdense regions where the progenitors of a typical high-redshift quasar host form and evolve. Our analysis shows that the peculiar conditions in such regions, i.e. strong halo clustering and high star formation rates, are crucial to produce a non-negligible number of massive seed BH host candidates: we find ≈1400 DH metal-free mini-haloes, including one of these which evolves to a synchronized pair and ends up in the massive quasar-host halo by z = 6. This demonstrates that the progenitors of high-redshift quasar host haloes can harbour early massive seed BHs. Our results further suggest that multiple massive seed BHs may form in or near the quasar host’s progenitors, potentially merging at lower redshifts and yielding gravitational wave events.
The population of supermassive black holes (SMBHs) is split between those that are quiescent, such as those seen in local galaxies including the Milky Way, and those that are active, resulting in ...quasars and active galactic nuclei (AGN). Outside our neighborhood, all the information we have on SMBHs is derived from quasars and AGN, giving us a partial view. We study the evolution of the SMBH population, total and active, by the continuity equation, backwards in time from z = 0 to z = 4. Type-1 and type-2 AGN are differentiated in our model on the basis of their respective Eddington ratio distributions, chosen on the basis of observational estimates. The duty cycle is obtained by matching the luminosity function of quasars, and the average radiative efficiency is the only free parameter in the model. For higher radiative efficiencies (≳ 0.07), a large fraction of the SMBH population, most of them quiescent, must already be in place by z = 4. For lower radiative efficiencies (~ 0.05), the duty cycle increases with the redshift and the SMBH population evolves dramatically from z = 4 onwards. The mass function of active SMBHs does not depend on the choice of the radiative efficiency or of the local SMBH mass function, but it is mainly determined by the quasar luminosity function once the Eddington ratio distribution is fixed. Only direct measurement of the total black-hole mass function at redshifts z ≳ 2 could break these degeneracies, offering important constraints on the average radiative efficiency. Focusing on type-1 AGN, for which observational estimates of the mass function and Eddington ratio distribution exist at various redshifts, models with lower radiative efficiencies better reproduce the high-mass end of the mass function at high z, but tend to over-predict it at low z, and vice-versa for models with higher radiative efficiencies.
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.
The growth efficiency of high-redshift black holes Pacucci, Fabio; Volonteri, Marta; Ferrara, Andrea
Monthly notices of the Royal Astronomical Society,
09/2015, Letnik:
452, Številka:
2
Journal Article
Recenzirano
Odprti dostop
The observational evidence that Super-Massive Black Holes (M
• ∼ 109–10 M⊙) are already in place less than 1 Gyr after the big bang poses stringent time constraints on the growth efficiency of their ...seeds. Among proposed possibilities, the formation of massive (∼103–6 M⊙) seeds and/or the occurrence of super-Eddington (
$\dot{M}>\dot{M}_{{\rm Edd}}$
) accretion episodes may contribute to the solution of this problem. In this work, using a set of astrophysically motivated initial conditions, we analytically and numerically investigate the accretion flow on to high-redshift (z ∼ 10) black holes to understand the physical requirements favouring rapid and efficient growth. Our model identifies a ‘feeding-dominated’ accretion regime and a ‘feedback-limited’ one, the latter being characterized by intermittent (duty cycles
${\cal D} \lesssim 0.5$
) and inefficient growth, with recurring outflow episodes. We find that low-mass seeds (≲103–4 M⊙) evolve in the feedback-limited regime, while more massive seeds (≳105–6 M⊙) grow very rapidly as they are found in the feeding-dominated regime. In addition to the standard accretion model with a fixed matter–energy conversion factor (ϵ = 0.1), we have also explored slim disc models, appropriate for super-Eddington accretion, where radiation is trapped in the disc and the radiative efficiency is reduced (ϵ ≲ 0.04), which may ensure a continuous growth with
$\dot{M} \gg \dot{M}_{{\rm Edd}}$
(up to
${\sim } 300\,\dot{M}_{{\rm Edd}}$
in our simulations). Under these conditions, outflows play a negligible role and a black hole can accrete 80–100 per cent of the gas mass of the host halo (∼107 M⊙) in ∼10 Myr, while in feedback-limited systems we predict that black holes can accrete only up to ∼15 per cent of the available mass.
Massive black hole (MBH) seeds at redshift z ≳ 10 are now thought to be key ingredients to explain the presence of the supermassive (109–10 M⊙) black holes in place <1 Gyr after the big bang. Once ...formed, massive seeds grow and emit copious amounts of radiation by accreting the left-over halo gas; their spectrum can then provide crucial information on their evolution. By combining radiation-hydrodynamic and spectral synthesis codes, we simulate the time-evolving spectrum emerging from the host halo of a MBH seed with initial mass 105 M⊙, assuming both standard Eddington-limited accretion, or slim accretion discs, appropriate for super-Eddington flows. The emission occurs predominantly in the observed infrared-submm (1-1000 μm) and X-ray (0.1–100 keV) bands. Such signal should be easily detectable by JWSTaround ∼ 1 μm up to z ∼ 25, and by ATHENA (between 0.1 and 10 keV, up to z ∼ 15). Ultra-deep X-ray surveys like the Chandra Deep Field South could have already detected these systems up to z ∼ 15. Based on this, we provide an upper limit for the z ≳ 6 MBH mass density of ρ• ≲ 2.5 × 102 M⊙ Mpc−3 assuming standard Eddington-limited accretion. If accretion occurs in the slim disc mode the limits are much weaker, ρ• ≲ 7.6 × 103 M⊙ Mpc−3 in the most constraining case.
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