Formation Of Supermassive Black Holes Research Articles

Studying the first galaxies with ALMA

We discuss observations of the first galaxies, within cosmic reionization, at centimeter and millimeter wavelengths. We present a summary of current observations of the host galaxies of the most distant QSOs (z∼6). These observations reveal the gas, dust, and star formation in the host galaxies on kpc-scales. These data imply an enriched ISM in the QSO host galaxies within 1 Gyr of the big bang, and are consistent with models of coeval supermassive black hole and spheroidal galaxy formation in major mergers at high redshift. Current instruments are limited to studying truly pathologic objects at these redshifts, meaning hyper-luminous infrared galaxies (L FIR ∼1013 L ⊙). ALMA will provide the one to two orders of magnitude improvement in millimeter astronomy required to study normal star forming galaxies (i.e. Ly-α emitters) at z∼6. ALMA will reveal, at sub-kpc spatial resolution, the thermal gas and dust—the fundamental fuel for star formation—in galaxies into cosmic reionization.

Near‐Infrared Adaptive Optics Imaging of High‐Redshift Quasars

The properties of high-redshift quasar host galaxies are studied in order to investigate the connection between galaxy evolution, nuclear activity, and the formation of supermassive black holes. We combine new near-IR observations of three high-redshift quasars ( -->2 MR ~ − 24.7 for the one radio-loud quasar, and -->MR ~ − 23.8 for the two radio-quiet quasars. When combined with existing data at lower redshift, these new observations depict a scenario where the host galaxies of radio-loud quasars are seen to follow the expected trend of luminous (~5L*) elliptical galaxies undergoing passive evolution. This trend is remarkably similar to that followed by radio galaxies at -->z > 1.5. Radio-quiet quasar hosts also follow a similar trend but at a lower average luminosity (~0.5 mag dimmer). The data indicate that quasar host galaxies are already fully formed at epochs as early as ~2 Gyr after the big bang and then passively fade in luminosity to the present epoch.

Formation and Evolution of Black Holes in Galactic Nuclei and Star Clusters

AbstractWe study the formation, growth, and co-evolution of single and multiple supermassive black holes (SMBHs) and compact objects like neutron stars, white dwarfs, and stellar mass black holes in galactic nuclei and star clusters, focusing on the role of stellar dynamics. In this paper we focus on one exemplary topic out of a wider range of work done, the study of orbital parameters of binary black holes in galactic nuclei (binding energy, eccentricity, relativistic coalescence) as a function of initial parameters. In some cases the classical evolution of black hole binaries in dense stellar systems drives them to surprisingly high eccentricities, which is very exciting for the emission of gravitational waves and relativistic orbit shrinkage. Such results are interesting to the emerging field of gravitational wave astronomy, in relation to a number of ground and space based instruments designed to measure gravitational waves from astrophysical sources (VIRGO, Geo600, LIGO, LISA). Our models self-consistently cover the entire range from Newtonian dynamics to the relativistic coalescence of SMBH binaries.

Gamma rays from dark matter minispikes in the Andromeda Galaxy M31

The existence of a population of wandering intermediate mass black holes (IMBHs) is a generic prediction of scenarios that seek to explain the formation of supermassive black holes in terms of growth from massive seeds. The growth of IMBHs may lead to the formation of DM overdensities called ''mini-spikes,'' recently proposed as ideal targets for indirect DM searches. Current ground-based gamma-ray experiments, however, cannot search for these objects due to their limited field of view, and it might be challenging to discriminate mini-spikes in the Milky Way from the many astrophysical sources that GLAST is expected to observe. We show here that gamma-ray experiments can effectively search for IMBHs in the nearby Andromeda Galaxy (also known as M31), where mini-spikes would appear as a distribution of point-sources, isotropically distributed in a {approx_equal}3 deg. circle around the galactic center. For a neutralinolike DM candidate with a mass m{sub {chi}}=150 GeV, up to 20 sources would be detected with GLAST (at 5{sigma}, in 2 months). With air Cherenkov telescopes such as MAGIC and VERITAS, up to 10 sources might be detected, provided that the mass of neutralino is in the TeV range or above.

Impact of astrophysical processes on the gamma-ray background from dark matter annihilations

We study the impact of astrophysical processes on the gamma-ray background produced by the annihilation of dark matter particles in cosmological halos, with particular attention to the consequences of the formation of supermassive black holes. In scenarios where these objects form adiabatically from the accretion of matter on small seeds, dark matter is first compressed into very dense ``spikes,'' then its density progressively decreases due to annihilations and scattering off of stellar cusps. With respect to previous analyses, based on nonevolving halos, the predicted annihilation signal is higher and significantly distorted at low energies, reflecting the large contribution to the total flux from unevolved spikes at high redshifts. The peculiar spectral feature arising from the specific redshift distribution of the signal, would discriminate the proposed scenario from more conventional astrophysical explanations. We discuss how this affects the prospects for detection and demonstrate that the gamma-ray background from dark matter (DM) annihilations might be detectable even in the absence of a signal from the Galactic center.

Supermassive Black Hole Formation through Rotational Instabilities

We investigate new paths to black hole formation by considering the general relativistic evolution of a differentially rotating polytrope with toroidal shape. We find that this polytrope is unstable to nonaxisymmetric modes, which leads to a fragmentation into self-gravitating, collapsing components. In the case of one such fragment, we apply a simplified adaptive mesh refinement technique to follow the evolution to the formation of an apparent horizon centered on the fragment. This is the first study of the one-armed instability in full general relativity.

The mass function of high-redshift seed black holes

Abstract In this Letter we derive the mass function of seed black holes that result from the central mass concentrated via disc accretion in collapsed haloes at redshift z ≈ 15. Using standard arguments including stability, we show that these pregalactic discs can assemble a significant mass concentration in the inner regions, providing fuel for the formation and initial growth of supermassive black holes. Assuming that these mass concentrations do result in central seed black holes, we determine the mass distribution of these seeds as a function of key halo properties. The seed mass distribution determined here turns out to be asymmetric and skewed to higher masses. Starting with these initial seeds, building up to 109 solar masses by z = 6 to power the bright quasars is not a problem in the standard Λ cold dark matter cosmogony. These seed black holes in gas-rich environments are likely to grow into the supermassive black holes at later times via mergers and accretion. Gas accretion on to these seeds at high redshift will produce miniquasars that likely play an important role in the reionization of the Universe. Some of these seed black holes, on the other hand, could be wandering in galaxy haloes as a consequence of frequent mergers, powering the off-nuclear ultra-luminous X-ray sources detected in nearby galaxies.

Reconstructing the Cosmic Evolution of Quasars from the Age Distribution of Local Early‐Type Galaxies

We use the spectra of 22,000 nearby early-type galaxies from the Sloan Digital Sky Survey (SDSS) to determine the age distribution of these galaxies as a function of their velocity dispersion sigma_v in the range 100 km/s < sigma_v < 280 km/s. We then combine the inferred age-distributions with the local abundance of spheroids, including early-type galaxies and late-type bulges, to predict the evolution of the quasar luminosity function (LF) in the redshift range 0<z<6. We make the following simple assumptions: (i) the formation of stars in each galaxy, at the epoch identified with the mean mass-weighted stellar age, is accompanied by the prompt assembly of the nuclear supermassive black hole (SMBH); (ii) the mass of the SMBH obeys the M_bh-sigma_v correlation observed in nearby galaxies; (iii) the SMBH radiates at a fraction f_Edd of the Eddington limit for a fixed duration t_Q, and is identified as a luminous quasar during this epoch, (iv) the intrinsic dispersions in the Eddington ratio and the M_bh-sigma_v relation produce a combined scatter of Delta(log L_Q) around the mean logarithmic quasar luminosity <log L_Q> at fixed sigma_v. These assumptions require that the SMBH remnants of quasars with bolometric luminosity below L_bol=10^{12.5} f_Edd L_sun reside predominantly in bulges of late type galaxies. We find that evolution of the observed quasar LF can be fit over the entire redshift range in this simple model, 0<z<6 with the choices of Delta(log L_Q)=0.6-0.9, t_Q= (6-8)x10^7 yr, and <f_Edd>=0.3-0.5. We find no evidence that any of the model parameters evolves with redshift, supporting the strong connection between the formation of stars and nuclear SMBHs in spheroids.

The Effect of Orbital Eccentricity on Gravitational Wave Background Radiation from Supermassive Black Hole Binaries

A compact binary in an eccentric orbit radiates gravitational waves (GWs) at all integer harmonics of its orbital frequency. In this study, we investigate the effect of orbital eccentricity on the expected gravitational background radiation (GWBR) from supermassive black hole (SMBH) binaries in the nuclei of galaxies. For this purpose, we formulate a power spectrum of the GWBR from cosmological evolving eccentric binaries. Then, we apply this formulation to the case of the GWBR from SMBH binaries. The key to doing this is to correctly estimate the number density of coalescing SMBH binaries. In this study, we use a semi-analytic model of galaxy and SMBH formation. We find that the power spectrum of the GWBR from SMBH binaries on eccentric orbits is suppressed for frequencies $f \lesssim 1~{\rm nHz}$ if the initial eccentricity, $e_0$, satisfies $e_0 > 0.2$ and the initial semi-major axis is 300 times Scwarzschild radius. Our model predicts that while the overall shape and amplitude of the power spectrum depend strongly on the processes of galaxy formation, the eccentricity of binaries can affect the shape of the power spectrum for lower frequencies, i.e., $f \lesssim 1~{\rm nHz}$. Pulsar timing measurements, which can detect GW in this frequency range, could constrain the effect of eccentricity on the power spectrum of the GWBR from SMBH binaries.

Gravitational Recoil Velocities from Eccentric Binary Black Hole Mergers

The formation and growth of supermassive black holes is a key issue to unveil the secrets of galaxy formation. In particular, the gravitational recoil produced in the merger of unequal mass black hole binaries could have a number of astrophysical implications, such as the ejection of black holes from the host galaxy or globular cluster. We present estimates of the recoil velocity that include the effect of small eccentricities. The approach is specially suited for the last stage of the merger, where most of the emission of linear momentum in gravitational waves takes place. Supplementing our estimates with post-Newtonian approximations, we obtain lower and upper bounds that constrain previous recoil velocities estimates as well as a best estimate that agrees with numerical simulations in the quasi-circular case. For eccentricities e <= 0.1, the maximum recoil is found for mass ratios of M_1/M_2 ~ 0.38 with a best estimate of ~ 167 (1 + e) km/s and upper and lower bounds of 79 (1 + e) km/s and 216 (1 + e) km/s respectively.

A Gravitational Instability-driven Viscosity in Self-gravitating Accretion Disks

We derive a viscosity from gravitational instability in self-gravitating accretion disks, which has the required properties to account for the observed fast formation of the first supermassive black holes in highly redshifted quasars and for the cosmological evolution of the black hole mass distribution.

A symbiotic scenario for the rapid formation of supermassive black holes

The most massive black holes, lurking at the centres of large galaxies, must have formedless than a billion years after the big bang, as they are visible today in the form of brightquasars at redshift larger than six. Their early appearance is mysterious, because theradiation pressure, generated by infalling ionized matter, inhibits the rapid growth of theseblack holes from stellar-mass black holes. It is shown that the supermassive black holes mayform timeously through the accretion of predominantly degenerate sterile neutrino darkmatter onto stellar-mass black holes. Our symbiotic scenario relies on the formation of,first, supermassive degenerate sterile neutrino balls through gravitational cooling and, then,stellar-mass black holes through supernova explosions of massive stars at the centre of theneutrino balls. The observed lower and upper limits of the supermassive black holesare explained by the corresponding mass limits of the preformed neutrino balls.

The luminosity function of high-redshift quasi-stellar objects. A combined analysis of GOODS and SDSS

Aims. In this work the luminosity function of QSOs is measured in the redshift range for the absolute magnitude interval . Determining the faint-end of the luminosity function at these redshifts provides important constraints on models of the joint evolution of galaxies and AGNs.Methods. We have defined suitable criteria to select faint QSOs in the GOODS fields, checking their effectiveness and completeness in detail. A spectroscopic follow-up of the resulting QSO candidates was carried out. The confirmed sample of faint QSOs is compared with a brighter one derived from the SDSS. We used a Monte-Carlo technique to estimate the properties of the luminosity function, checking various parameterizations for its shape and evolution.Results. Models based on pure density evolution show better agreement with observation than do models based on pure luminosity evolution. However, a different break magnitude with respect to is required at . Models with a steeper faint-end score a higher probability. We do not find any evidence for a bright-end flattening at redshift .Conclusions. The estimated space density evolution of QSOs indicates a suppression of the formation and/or feeding of supermassive black holes at these redshifts. The QSO contribution to the UV background is insufficient for ionizing the IGM at .

Supermassive black hole formation during the assembly of pre-galactic discs

In this paper, we discuss the evolution of gravitationally unstable pre-galactic discs that result from the collapse of haloes at high redshift z≈ 10 or so, which have not yet been enriched by metals. In cases where molecular hydrogen formation is suppressed, the discs are maintained at a temperature of a few thousand Kelvin. However, when molecular hydrogen is present, cooling can proceed down to a few hundred Kelvin. Analogous to the case of the larger-scale protogalactic discs, we assume that the evolution of these discs is mainly driven by angular momentum redistribution induced by the development of gravitational instabilities in the disc. We also properly take into account the possibility of disc fragmentation. We thus show that this simple model naturally predicts the formation of supermassive black holes in the nuclei of such discs and provides a robust determination of their mass distribution as a function of halo properties. We estimate that roughly 5 per cent of discs resulting from the collapse of haloes with M≈ 107 M⊙ should host a massive black hole with a mass MBH≈ 105 M⊙. We confirm our arguments with time-dependent calculations of the evolution of the surface density and of the accretion rate in these primordial discs. The luminosity of the outer, colder disc is expected to be very low (in the range of a few thousand L⊙), while the formation of the black hole is expected to produce a burst with a luminosity of a few times 109 L⊙. This mechanism offers an efficient way to form seed black holes at high redshift. The predicted masses for our black hole seeds enable the comfortable assembly of 109-M⊙ black holes powering the luminous quasars detected by the Sloan Digital Sky Survey at z= 6 for a concordance cosmology.

Formation of supermassive black holes by direct collapse in pre-galactic haloes

We describe a mechanism by which supermassive black holes (SMBHs) can form directly in the nuclei of protogalaxies, without the need for 'seed' black holes left over from early star formation. Self-gravitating gas in dark matter haloes can lose angular momentum rapidly via runaway, global dynamical instabilities, the so-called 'bars within bars' mechanism. This leads to the rapid build-up of a dense, self-gravitating core supported by gas pressure - surrounded by a radiation pressure-dominated envelope - which gradually contracts and is compressed further by subsequent infall. We show that these conditions lead to such high temperatures in the central region that the gas cools catastrophically by thermal neutrino emission, leading to the formation and rapid growth of a central black hole. We estimate the initial mass and growth rate of the black hole for typical conditions in metal-free haloes with T vir ∼ 10 4 K, which are the most likely to be susceptible to runaway infall. The initial black hole should have a mass of?20 M ⊙ , but in principle could grow at a super-Eddington rate until it reaches ∼10 4 10 6 M ⊙ . Rapid growth may be limited by feedback from the accretion process and/or disruption of the mass supply by star formation or halo mergers. Even if super-Eddington growth stops at ∼10 3 -10 4 M ⊙ , this process would give black holes ample time to attain quasar-size masses by a redshift of 6, and could also provide the seeds for all SMBHs seen in the present Universe.

Formation of Supermassive Black Holes through Fragmentation of Torodial Supermassive Stars

We investigate new paths to supermassive black hole formation by considering the general relativistic evolution of a differentially rotating polytrope with a toroidal shape. We find that this polytrope is unstable to nonaxisymmetric modes, which leads to a fragmentation into self-gravitating, collapsing components. In the case of one such fragment, we apply a simplified adaptive mesh refinement technique to follow the evolution to the formation of an apparent horizon centered on the fragment. This is the first study of the onset of nonaxisymmetric dynamical instabilities of supermassive stars in full general relativity.

Testing Models of Supermassive Black Hole Seed Formation through Gravity Waves

We study the gravitational wave background produced from the formation and assembly of supermassive black holes within the cosmological paradigm of hierarchical structure formation. In particular, we focus on a supermassive black hole formation scenario in which the present-day population of supermassive black holes is built from high-mass seed black holes and we compute the concomitant spectrum of gravitational radiation produced by mergers of the seed black holes. We find that this scenario predicts a large, gravitational wave background that should be resolved into individual sources with space interferometers such as the proposed Laser Interferometric Space Antenna (LISA). The number of inspiral, merger and ringdown events above a signal to noise ratio of 5 that result from massive black hole seeds is of order 10^3. This prediction is robust and insensitive to several of the details of the model. We conclude that an interferometer such as LISA will be able to effectively rule out or confirm a class of models where supermassive black holes grow from high-mass seed black holes and may be able to place strong limits on the role of mergers as a channel for supermassive black hole growth. Supermassive black hole seeds likely form in the earliest proto-galactic structures at high redshift and the masses of supermassive black holes are known to be strongly correlated with the potentials of the spheroids in which they reside, therefore these results imply that space interferometers can be used as a powerful probe of the physics of galaxy formation and proto-galaxy formation at very high redshift.

Metal Enrichment of the Intergalactic Medium and Production of Massive Black Holes

A model for the chemical evolution of the intergalactic medium (IGM) is presented using theoretical yields of very massive stars (VMSs; M_(VMS) > 100 M_☉) and Type II supernovae (SNe II). It is shown that if [Si/C] is indeed as high as ~0.7 in the IGM, then VMSs (M_(VMS) ≈ 140-260 M_☉) associated with pair-instability supernovae (PI-SNe) in low-mass (~10^5 M_☉) halos at high redshift must produce at least 50% of the Si. The remainder is from later galactic outflows of SN II debris, which also provide most of the C and O. Both sources are required to account for the metal inventory in the IGM. The early VMS production must continue until redshift z ~ 15 so that the efficiency of VMS formation per low-mass halo is significantly below unity. Contributions from the later galactic outflows mainly occur at z ~ 4-6. Using a Salpeter initial mass function, we infer that the number of VMSs (M_(VMS) ≈ 260-2000 M_☉) producing massive black holes (MBHs) with an average mass 〈M_(MBH)〉 ~ 270-550 M_☉ is ≈0.72 times the number of VMSs associated with PI-SNe. The amount of metals (particularly Si) in the IGM that is attributable to PI-SNe is thus closely coupled with the total mass of MBHs produced in epochs prior to galaxy formation. Production of ~50% of the Si in the IGM by PI-SNe corresponds to an early inventory of MBHs that constitutes a fraction ~(4-8) × 10^(-5) of the total baryonic mass in the universe. This is comparable to the global mass budget of the central supermassive black holes (SMBHs) in present-day galaxies. The corresponding occurrence rates in each halo of ~10^5 M_☉ during the epoch of VMS formation at z ≳ 15 are ~0.9 Gyr^(-1) for VMSs associated with PI-SNe and ~0.6 Gyr^(-1) for the concomitant more massive stars producing MBHs. These rates may be of use to studies of H_2 dissociation and reionization and to models of SMBH formation.

Forming supermassive black holes by accreting dark and baryon matter

Given a large-scale mixture of self-interacting dark matter (SIDM) particles and baryon matter distributed in the early Universe, we advance here a two-phase accretion scenario for forming supermassive black holes (SMBHs) with masses around ∼109 M⊙ at high redshifts z(⋆6). The first phase is conceived to involve a rapid quasi-spherical and quasi-steady Bondi accretion of mainly SIDM particles embedded with baryon matter on to seed black holes (BHs) created at redshifts z≲ 30 by the first generation of massive Population III stars; this earlier phase rapidly gives birth to significantly enlarged seed BH masses of during z∼ 20-15, where σ0 is the cross-section per unit mass of SIDM particles and Cs is the velocity dispersion in the SIDM halo referred to as an effective ‘sound speed'. The second phase of BH mass growth is envisaged to proceed primarily via baryon accretion, eventually leading to SMBH masses of MBH∼ 109 M⊙; such SMBHs may form either by z∼ 6 for a sustained accretion at the Eddington limit or later at lower z for sub-Eddington mean accretion rates. In between these two phases, there is a transitional yet sustained diffusively limited accretion of SIDM particles which in an eventual steady state would be much lower than the accretion rates of the two main phases. We intend to account for the reported detections of a few SMBHs at early epochs, e.g. Sloan Digital Sky Survey (SDSS) 1148+5251 and so forth, without necessarily resorting to either super-Eddington baryon accretion or very frequent BH merging processes. Only extremely massive dark SIDM haloes associated with rare peaks of density fluctuations in the early Universe may harbour such early SMBHs or quasars. Observational consequences are discussed. During the final stage of accumulating a SMBH mass, violent feedback in circumnuclear environs of a galactic nucleus leads to the central bulge formation and gives rise to the familiar empirical MBH−σb correlation inferred for nearby normal galaxies with σb being the stellar velocity dispersion in the galactic bulge; in our scenario, the central SMBH formation precedes that of the galactic bulge.

Spin, Accretion, and the Cosmological Growth of Supermassive Black Holes

If supermassive black holes (SMBHs) are the energy sources that power quasars and active galactic nuclei (AGNs), then QSO SDSS 1148+5251, the quasar with the highest redshift (zQSO = 6.43), hosts an SMBH formed within ~0.9 Gyr after the big bang. This requirement places constraints on the cosmological formation of SMBHs, believed to grow from smaller initial seeds by a combination of accretion and mergers. We focus on gas accretion onto seeds produced by the collapse of Population III stars at high redshift. We incorporate the results of recent relativistic, MHD simulations of disk accretion onto Kerr black holes to track the coupled evolution of the masses and spins of the holes. We allow for an additional amplification of ~104 in the mass of a typical seed due to mergers, consistent with recent Monte Carlo simulations of hierarchical mergers of cold dark matter halos containing black hole seeds. We find that the growth of Population III black hole remnants to ~109 M☉ by zQSO ≳ 6.43 favors MHD accretion disks over standard thin disks. MHD disks tend to drive the holes to a submaximal equilibrium spin rate a/M ~ 0.95 and radiation efficiency ϵM ~ 0.2, while standard thin disks drive them to maximal spin (a/M = 1) and efficiency (ϵM = 0.42). This small difference in efficiency results in a huge difference in mass amplification by accretion at the Eddington limit. The MHD equilibrium efficiency is consistent with the observed ratio of the QSO plus AGN luminosity density to the local SMBH mass density. Our prototype analysis is designed to stimulate the incorporation of results from relativistic stellar collapse and MHD accretion simulations in future Monte Carlo simulations of hierarchical structure formation to better determine the cosmological role of SMBHs and their mass and spin distributions.