Presence Of Supermassive Black Holes Research Articles

EPOCHS Paper V. The dependence of galaxy formation on galaxy structure at z < 7 from JWST observations

ABSTRACT We measure the broad impact of galaxy structure on galaxy formation by examining the ongoing star formation and integrated star formation history as revealed through the stellar masses of galaxies at z < 7 based on JWST CEERS data from the Extended Groth Strip (EGS). Using the morphological catalog of 3965 visually classified JWST galaxies from Ferreira et al. (2023), we investigate the evolution of stars, and when they form, as a function of morphological type as well as galaxies classified as passive and starburst through spectral energy distributions. Although disc galaxies dominate the structures of galaxies at z < 7, we find that these discs are in general either ‘passive’, or on the main sequence of star formation, and do not contain a large population of starburst galaxies. We also find no significant correlation between morphological type and the star formation rate or colours of galaxies at z < 7. In fact, we find that the morphologically classified ‘spheroids’ tend to be blue and are not found to be predominately passive systems at z > 1.5. We also find that the stellar mass function for disc galaxies does not evolve significantly during this time, whereas other galaxy types, such as the peculiar population, evolve dramatically, declining at lower redshifts. This indicates that massive peculiars are more common at higher redshifts. We further find that up to z ∼ 7, the specific star formation rate (sSFR) does not vary with visual morphology, but strongly depends on stellar mass and internal galaxy mass density. This demonstrates that at early epochs galaxy assembly is a mass-driven, rather than a morphologically driven process. Quenching of star formation is therefore a mass-dominated process throughout the universe’s history, likely due to the presence of supermassive black holes.

Formation of Massive Black Holes with M = (103–108) M ⊙ at Pre-quasar Epochs through Hoyle–Lyttleton–Bondi Accretion of Self-interacting Dark Matter onto a Moving Seed

The presence of supermassive black holes with M ∼ 109 M ⊙ hosted by the luminous quasars at cosmological redshift z ≥ 6 is still an open problem in astrophysical cosmology. Here we study the formation of massive black holes at high redshift (z ≫ 7) through Hoyle–Lyttleton–Bondi accretion of self-interacting dark matter (SIDM) onto a 20 M ⊙ seed black hole moving with a velocity ∼100 km s−1 inside the short, mean-free path region of an SIDM halo. We consider observational constraints on a specific SIDM cross section, σ/m dm = (0.1–5) cm2 g−1. Formation timescale of massive black holes with M = (103–108) M ⊙ is calculated for the universal Navarro–Frenk–White (NFW) profile, singular isothermal sphere (SIS), other power-law profiles with a cusp index 2.19 ≤ γ ≤ 2.5 of accreted dark matter, and modified-core isothermal profiles. The ambient sound speed is taken as C s = (10–100) km s−1. It is found that an NFW profile with halo concentration C = 4.75–32.58 estimated at z = 20 and 30 for halo masses M 200 = (1012–1014) M ⊙ favors formation of massive black holes with M = (103–108) M ⊙ at high redshift, well before quasar epoch. In this profile, these black holes grow within timescales (0.1–69) Myr at z = 16–20. For the SIS profile, the black hole formation timescales are short compared to NFW. For power-law profiles, massive black holes with M = (106–108) M ⊙ grow within a few tens to 100 Myr (z = 5–30). For modified-core isothermal profiles, the timescale of massive black hole formation is in the range (0.79–464.08) Myr (z = 8–30).

Warm Dark Matter Galaxies with Central Supermassive Black Holes

We generalize the Thomas–Fermi approach to galaxy structure to include central supermassive black holes and find, self-consistently and non-linearly, the gravitational potential of the galaxy plus the central black hole (BH) system. This approach naturally incorporates the quantum pressure of the fermionic warm dark matter (WDM) particles and shows its full power and clearness in the presence of supermassive black holes. We find the main galaxy and central black hole magnitudes as the halo radius rh, halo mass Mh, black hole mass MBH, velocity dispersion σ, and phase space density, with their realistic astrophysical values, masses and sizes over a wide galaxy range. The supermassive black hole masses arise naturally in this framework. Our extensive numerical calculations and detailed analytic resolution of the Thomas–Fermi equations show that in the presence of the central BH, both DM regimes—classical (Boltzmann dilute) and quantum (compact)—do necessarily co-exist generically in any galaxy, from the smaller and compact galaxies to the largest ones. The ratio R(r) of the particle wavelength to the average interparticle distance shows consistently that the transition, R≃1, from the quantum to the classical region occurs precisely at the same point rA where the chemical potential vanishes. A novel halo structure with three regions shows up: in the vicinity of the BH, WDM is always quantum in a small compact core of radius rA and nearly constant density; in the region rA<r<ri until the BH influence radius ri, WDM is less compact and exhibits a clear classical Boltzmann-like behavior; for r>ri, the WDM gravity potential dominates, and the known halo galaxy shows up with its astrophysical size. DM is a dilute classical gas in this region. As an illustration, three representative families of galaxy plus central BH solutions are found and analyzed: small, medium and large galaxies with realistic supermassive BH masses of 105M⊙, 107M⊙ and 109M⊙, respectively. In the presence of the central BH, we find a minimum galaxy size and mass Mhmin≃107M⊙, larger (2.2233×103 times) than the one without BH, and reached at a minimal non-zero temperature Tmin. The supermassive BH heats up the DM and prevents it from becoming an exactly degenerate gas at zero temperature. Colder galaxies are smaller, and warmer galaxies are larger. Galaxies with a central black hole have large masses Mh>107M⊙>Mhmin; compact or ultracompact dwarf galaxies in the range 104M⊙<Mh<107M⊙ cannot harbor central BHs. We find novel scaling relations MBH=DMh38 and rh=CMBH43, and show that the DM galaxy scaling relations Mh=bΣ0rh2 and Mh=aσh4/Σ0 hold too in the presence of the central BH, Σ0 being the constant surface density scale over a wide galaxy range. The galaxy equation of state is derived: pressure P(r) takes huge values in the BH vicinity region and then sharply decreases entering the classical region, following consistently a self-gravitating perfect gas P(r)=σ2ρ(r) behavior.

From the Editors

Welcome to the third volume of JoAE. Similar to the previous two editorials, here we offer an update regarding the journal, as well as ponder one of the stupefying dilemmas we have encountered: the “So What?” question.Last year we found ourselves in some manuscript submission conundrums. The primary issue involved the processing of manuscripts. As of this writing (September 2021), we have 90+ submissions for this year, and more than 200 manuscripts in some form of revision or review from the previous two years. Using Google’s G Suite for manuscript submission and correspondence was not sustainable. We needed to evolve.We migrated to the web-based journal management system Scholastica. We made some beginners’ mistakes, but the system makes organizing submissions quicker and easier. Moreover, we felt we were overwhelming our editorial board and ad hoc reviewers. After consultation with experienced journal editors, we began issuing more “desk rejects.” If manuscripts do not follow submission guidelines1 and/or disregards our previous editors’ introductions2 or the JoAE blog,3 we no longer send them out for peer review. We appreciate our reviewers and want to protect their time and effort; they offer their passion and unpaid labor to make this journal go.Another issue was the overwhelming number of COVID-19 submissions. We made the decision to reject a majority of these. Why? Most were chronologies: “This happened, and this happened, and this happened.” They did not satisfy the showing-telling characteristic of solid autoethnographic writing. Moreover, while providing personal experience, a majority of manuscripts did not answer the all-important “So What?” question: Why does (or should) your experience matter to others? Why should readers care about your issues and experiences? For COVID-19 manuscripts, we believe the So What? question was (is) difficult to answer because we are all still living with the pandemic.4The “So What?” dilemma was not just a challenge for COVID-19 submissions. Many submissions we desk rejected also did not answer the “So What?” question. In some manuscripts it was not clear if the author even considered the “So What?” question. Therefore, in this editorial, we thought it would be meaningful to consider the “So What?” question not only for JoAE but for autoethnographic research in general.5We reflected on why some autoethnographers appear to have difficulty answering the “So What?” question. We suggest that to answer the question, autoethnographers need to seriously consider four “How” questions:This list is not all-encompassing, nor do all the “how” questions need to be answered to fully answer the “So What?” question.Answering the “So What?” question is clearer when pursuing research in the sciences. “This analysis is the first in the United States to assess COVID-19 vaccination coverage among pregnant women.”8 This statement (and article) has obvious important health care implications. The Event Horizon Telescope Collaboration answered the “So What?” question when they showed “Our radio-wave observations thus provide powerful evidence for the presence of supermassive black holes in centers of galaxies and as the central engines of active galactic nuclei.”9 They are moving physics forward. Even in traditional quantitative and qualitative social science research, the “So What?” question is more easily answered. “Group identification and stream familiarity were found to be positively related to perceived credibility. These findings hold implications for using video game streams as a marketing tool…”10 But, for autoethnography, answering the question requires much more skill, deliberation, and nuance.We want to publish articles that use autoethnography to add to understandings of the complexities of personal and social experience. Or manuscripts that add to or complicate our understandings of the philosophical underpinnings of autoethnography. Or manuscripts that examine new subjects through an autoethnographic lens. The “So What?” question is critical, and authors must show and tell why their research is important and necessary, as well as why we, readers, should care about their work. Insightful and nuanced answers and analyses will help steer manuscripts away from a dreary desk reject

Small-scale primordial fluctuations in the 21 cm Dark Ages signal

ABSTRACT Primordial black hole production in the mass range $10\!-\!10^4 \, {\rm M_\odot}$ is motivated respectively by interpretations of the LIGO/Virgo observations of binary black hole mergers and by their ability to seed intermediate black holes that would account for the presence of supermassive black holes at very high redshift. Their existence would imply a boost in the primordial power spectrum if they were produced by overdensities reentering the horizon and collapsing after single-field inflation. This, together with their associated Poisson fluctuations would cause a boost in the matter power spectrum on small scales. The extra power could become potentially observable in the 21 cm power spectrum on scales around $k\sim 0.1\!-\!50\, {\rm Mpc^{-1}}$ with the new generation of filled low-frequency interferometers. We explicitly include the contribution from primordial fluctuations in our prediction of the 21 cm signal that has been previously neglected, by constructing primordial power spectra motivated by single-field models of inflation that would produce extra power on small scales. We find that depending on the mass and abundance of primordial black holes, it is important to include this contribution from the primordial fluctuations, so as not to underestimate the 21 cm signal. Evidently our predictions of detectability, which lack any modelling of foregrounds, are unrealistic, but we hope that they will motivate improved cleaning algorithms that can enable us to access this intriguing corner of primordial black hole-motivated parameter space.

Direct collapse to supermassive black hole seeds: the critical conditions for suppression of H2 cooling

ABSTRACT Observations of high-redshift quasars imply the presence of supermassive black holes (SMBHs) already at $z$ ∼ 7.5. An appealing and promising pathway to their formation is the direct collapse scenario of a primordial gas in atomic-cooling haloes at $z$ ∼ 10–20, when the $\rm H_{2}$ formation is inhibited by a strong background radiation field, whose intensity exceeds a critical value, Jcrit. To estimate Jcrit, typically, studies have assumed idealized spectra, with a fixed ratio of $\rm H_{2}$ photodissociation rate $k_{\rm H_2}$ to the $\rm H^-$ photodetachment rate $k_{\rm H^-}$. This assumption, however, could be too narrow in scope as the nature of the background radiation field is not known precisely. In this work we argue that the critical condition for suppressing the H2 cooling in the collapsing gas could be described in a more general way by a combination of $k_{\rm H_2}$ and $k_{\rm H^-}$ parameters, without any additional assumptions about the shape of the underlying radiation spectrum. By performing a series of cosmological zoom-in simulations covering a wide range of relevant $k_{\rm H_2}$ and $k_{\rm H^-}$ parameters, we examine the gas flow by following evolution of basic parameters of the accretion flow. We test under what conditions the gas evolution is dominated by $\rm H_{2}$ and/or atomic cooling. We confirm the existence of a critical curve in the $k_{\rm H_2}{\!-\!}k_{\rm H^-}$ plane and provide an analytical fit to it. This curve depends on the conditions in the direct collapse, and reveals domains where the atomic cooling dominates over the molecular cooling. Furthermore, we have considered the effect of $\rm H_{2}$ self-shielding on the critical curve, by adopting three methods for the effective column density approximation in $\rm H_{2}$. We find that the estimate of the characteristic length scale for shielding can be improved by using λJeans25, which is 0.25 times that of the local Jeans length, which is consistent with previous one-zone modelling.

Submillimeter Signatures from Growing Supermassive Black Holes before Reionization

Abstract The presence of supermassive black holes (SMBHs) with masses up to M • ∼ 109 M ⊙ at redshifts z ≃ 7.5 suggests that their seeds may have started to grow long before the reionization in ambient medium with pristine chemical composition. During their latest 500 Myr episode of growing from z ≥ 10 to z ∼ 7, the black holes shone as luminous as 1011–1012 L ⊙, with a cumulative spectrum consisting of the intrinsic continuum from the hot accretion disk, nebular hydrogen, and helium spectral lines, and the free–free continuum from the gas of host halos. Here we address the question of whether such a plain spectrum would allow us to trace the evolution of these growing SMBHs. In our calculations we assume that host galaxies have stellar populations with masses smaller than the masses of their central black holes—the so-called obese black hole galaxies. Within this model we show that for a sufficiently high mass of gas in a host galaxy—not smaller than the mass of a growing black hole, the cumulative spectrum in the far-infrared reveals a sharp transition from a quasi-blackbody Rayleigh–Jeans spectrum of the black hole ∝λ −2 to a flat free–free nebular continuum λ 0.118 on a longer wavelength limit. Once such a transition in the spectrum is resolved, the black hole mass can be inferred as a combination of the observed wavelength at the transition λ k and the corresponding spectral luminosity. The possible observability of this effect in spectra of growing high-z SMBHs and determination of their mass with the upcoming James Webb Space Telescope and the planned space project Spektr-M is briefly discussed.

Ultralight Thomas-Fermi dark matter

We investigate the viability of a simple dark matter (DM) model consisting of a single fermion in the context of galactic dynamics. We use a consistent approach that does not presume a particular DM density profile but instead requires that the DM+baryon system is in hydrostatic equilibrium. Using a phenomenological baryon density profile, the model then predicts the DM distribution with a core like behavior close to the galactic center. The presence of supermassive black holes (SMBHs) in the center of large galaxies arises naturally in this framework. Using data from a set of large elliptical and spiral galaxies, and from a small set of dwarf galaxies, we find that the model can explain most of the bulk galactic properties, as well as some of the features observed in the rotation curves, provided the DM mass is in the $\mathcal{O}$(50 eV) range. More precise tests of the model require better modeling of the baryon profile and better control on the uncertainties in the data.

Intermittent fragmentation and statistical variations during gas collapse in magnetized atomic cooling haloes

Observations reveal the presence of supermassive black holes (SMBH) as early as ~700 million years after the Big Bang. Their formation path is still subject to current debate. We explore the influence of magnetic fields, which are strongly amplified via the turbulent small-scale dynamo, on the formation of SMBH seeds within the direct collapse scenario. In this study, we perform for the first time cosmological magnetohydrodynamic large eddy simulations that employ a model for unresolved, compressible MHD turbulence. In total we perform 36 simulations for 9 haloes each with two different initial magnetic field strengths, and with and without employing the unresolved turbulence model. We make use of the adaptive mesh refinement approach to achieve an effective spatial resolution of less than one proper astronomical unit. We consider a regime where cooling is regulated by atomic hydrogen and the molecular hydrogen gets dissociated by a strong radiation field. Our main finding is that the majority of the gas properties in the haloes at the final output are predominantly determined by the run-away gravitational collapse. Turbulence is supersonic and super-Alfv\'enic in all cases, and magnetic fields are amplified to an approximately dynamically relevant regime. Finally, fragmentation during the collapse is intermittent and mass accretion rates range from 0.2-3 Msun/yr. This suggests that the presence of strongly amplified magnetic fields and turbulence provides additional pressure support on small scales and make the direct collapse a viable scenario for the formation of massive objects under the required ambient conditions.

First M87 Event Horizon Telescope Results. I. The Shadow of the Supermassive Black Hole

Abstract When surrounded by a transparent emission region, black holes are expected to reveal a dark shadow caused by gravitational light bending and photon capture at the event horizon. To image and study this phenomenon, we have assembled the Event Horizon Telescope, a global very long baseline interferometry array observing at a wavelength of 1.3 mm. This allows us to reconstruct event-horizon-scale images of the supermassive black hole candidate in the center of the giant elliptical galaxy M87. We have resolved the central compact radio source as an asymmetric bright emission ring with a diameter of 42 ± 3 μas, which is circular and encompasses a central depression in brightness with a flux ratio ≳10:1. The emission ring is recovered using different calibration and imaging schemes, with its diameter and width remaining stable over four different observations carried out in different days. Overall, the observed image is consistent with expectations for the shadow of a Kerr black hole as predicted by general relativity. The asymmetry in brightness in the ring can be explained in terms of relativistic beaming of the emission from a plasma rotating close to the speed of light around a black hole. We compare our images to an extensive library of ray-traced general-relativistic magnetohydrodynamic simulations of black holes and derive a central mass of M = (6.5 ± 0.7) × 109 M ⊙. Our radio-wave observations thus provide powerful evidence for the presence of supermassive black holes in centers of galaxies and as the central engines of active galactic nuclei. They also present a new tool to explore gravity in its most extreme limit and on a mass scale that was so far not accessible.

The Delay Time Distribution of Tidal Disruption Flares

Recent observations suggest that stellar tidal disruption events (TDE) are strongly overrepresented in rare, post-starburst galaxies. Several dynamical mechanisms have been proposed to elevate their TDE rates, ranging from central stellar overdensities to the presence of supermassive black hole (SMBH) binaries. Another such mechanism, introduced here, is a radial velocity anisotropy in the nuclear star cluster produced during the starburst. These, and other, dynamical hypotheses can be disentangled by comparing observations to theoretical predictions for the TDE delay time distribution (DTD). We show that SMBH binaries are a less plausible solution for the post-starburst preference, as they can only reproduce the observed DTD with extensive fine-tuning. The overdensity hypothesis produces a reasonable match to the observed DTD (based on the limited data currently available), provided that the initial stellar density profile created during the starburst, $\rho(r)$, is exceptional in both steepness and normalization. In particular, explaining the post-starburst preference requires $\rho \propto r^{-\gamma}$ with $\gamma \gtrsim 2.5$, i.e. much steeper than the classic Bahcall-Wolf equilibrium profile of $\gamma = 7/4$. For "ultrasteep" density cusps ($\gamma \ge 9/4$), we show that the TDE rate decays with time measured since the starburst as $\dot{N} \propto t^{-(4\gamma-9)/(2\gamma-3)} / \ln t$. Radial anisotropies also represent a promising explanation, provided that initial anisotropy parameters of $\beta_0 \approx 0.5$ are sustainable against the radial orbit instability. TDE rates in initially anisotropic cusps will decay roughly as $\dot{N} \propto t^{-\beta_0}$. As the sample of TDEs with well-studied host galaxies grows, the DTD will become a powerful tool for constraining the exceptional dynamical properties of post-starburst galactic nuclei.

Formation of Supermassive Black Hole Seeds

AbstractThe detection of quasars at z > 6 unveils the presence of supermassive black holes of a few billion solar masses. The rapid formation process of these extreme objects remains a fascinating and open issue. Such discovery implies that seed black holes must have formed early on, and grown via either rapid accretion or BH/galaxy mergers. In this theoretical review, we discuss in detail various BH seed formation mechanisms and the physical processes at play during their assembly. We discuss the three most popular BH formation scenarios, involving the (i) core-collapse of massive stars, (ii) dynamical evolution of dense nuclear star clusters, (iii) collapse of a protogalactic metal free gas cloud. This article aims at giving a broad introduction and an overview of the most advanced research in the field.

Major Advances in Radio Astronomy: Some Key Questions Today

During the last six decades, several outstanding discoveries have been made in the field of radio astronomy. These have revolutionized our understanding of the mysteries of the Universe. Observations of radio galaxies and quasars that emit extremely powerful radio waves indicate presence of supermassive black holes at their centre. Discovery and detailed observations of the 2.7 K cosmic microwave background temperature have provided strong support to the Big Bang Model of the Universe, giving tight constraints on the relative contributions of baryons, dark matter and dark energy in the Universe. Observations of the emission line of neutral hydrogen from spiral galaxies provide information about the formation and evolution of galaxies. Over 150 molecules have been discovered in the interstellar medium, giving details about the physics and chemistry of the interstellar space; these are also ingredients of life in the Universe. Discovery of Pulsating Radio Sources (Pulsars) have provided strong support to the models of neutron stars that are end products of a star when its ‘nuclear fuel’ runs out. Observations of Pulsars also provide tests of the General Theory of Relativity. I also summarize some of the investigations that are being carried out currently with the Ooty Radio Telescope in South India and with the Giant Metrewave Radio Telescope near Pune; these are amongst the largest radio telescopes in the world. Finally, I describe some of the Key Questions today.

A supermassive black hole in an ultra-compact dwarf galaxy.

Ultra-compact dwarf galaxies are among the densest stellar systems in the Universe. These systems have masses of up to 2×10(8) solar masses, but half-light radii of just 3-50parsecs. Dynamical mass estimates show that many such dwarfs are more massive than expected from their luminosity. It remains unclear whether these high dynamical mass estimates arise because of the presence of supermassive black holes or result from a non-standard stellar initial mass function that causes the average stellar mass to be higher than expected. Here we report adaptive optics kinematic data of the ultra-compact dwarf galaxy M60-UCD1 that show a central velocity dispersion peak exceeding 100kilometres per second and modest rotation. Dynamical modelling of these data reveals the presence of a supermassive black hole with a mass of 2.1×10(7) solar masses. This is 15 per cent of the object's total mass. The high black hole mass and mass fraction suggest that M60-UCD1 is the stripped nucleus of a galaxy. Our analysis also shows that M60-UCD1's stellar mass is consistent with its luminosity, implying a large population of previously unrecognized supermassive black holes in other ultra-compact dwarf galaxies.

Milliarcsec-scale radio emission of ultraluminous X-ray sources: steady jet emission from an intermediate-mass black hole?

The origin of the high X-ray luminosities of most ultraluminous X-ray sources (ULXs) still remains poorly understood. Most of the scenarios proposed to explain their nature assume that ULXs are powered by accretion on to a black hole (BH). In this case, the detection of compact radio emission and the location of the ULXs in the Fundamental Plane (X-ray versus radio-luminosity plane) can provide an estimate of the ULX BH mass and help address the question of their physical nature. We present the results of a high-resolution (very long baseline interferometry) radio observational campaign aimed at detecting and studying compact radio emission in four ULXs with known radio counterparts. We find that one of the targets (N4559-X4) was previously misclassified: its low X-ray luminosity indicates that the source is not a ULX. No milliarcsec-scale radio emission is detected for N4559-X4 nor for the ULXs N4490-X1 and N5194-X2, for which upper limits on the radio luminosities are estimated. These limits argue strongly against the presence of supermassive BHs in these three systems. For N4559-X4, the low X-ray luminosity and the ratio of the radio and X-ray luminosities suggest the presence of an X-ray binary. Compact radio emission is detected for the ULX N5457-X9 within its \textit{Chandra} positional error, making N5457-X9 a potential intermediate-mass BH with steady jet emission.

A new probe of black holes and their environment: Luminous flares from tidally disrupted stars

AbstractThe luminous accretion flares from tidally disrupted stars represent a powerful probe of the presence of supermassive black holes (SMBHs) in otherwise non-active galaxies, of accretion physics and BH spin, of jet formation, and relativistic effects. Further, the reprocessing of the continuum radiation of the flare into IR, optical and UV emission lines provides us with multiple new diagnostics of the properties of any gaseous material in the vicinity of the SMBH and in the host galaxy itself. While first events were discovered in the course of the ROSAT all-sky survey in X-rays, the last few years have seen the detection of several more flares, including in the UV, optical and radio band and via their emission-line “echoes”. A wealth of applications will become feasible in upcoming years, once flares are detected in large numbers in current and future sky surveys.

Formation ofz∼6 Quasars from Hierarchical Galaxy Mergers

The discovery of luminous quasars at redshift z ~ 6 indicates the presence of supermassive black holes (SMBHs) of mass ~109 M? when the universe was less than 1 billion years old. This finding presents several challenges for theoretical models because whether such massive objects can form so early in the ?CDM cosmology, the leading theory for cosmic structure formation, is an open question. Furthermore, whether the formation process requires exotic physics such as super-Eddington accretion remains undecided. Here we present the first multiscale simulations that, together with a self-regulated model for the SMBH growth, produce a luminous quasar at z ~ 6.5 in the ?CDM paradigm. We follow the hierarchical assembly history of the most massive halo in a ~3 Gpc3 volume and find that this halo of ~8 ? 1012 M? forming at z ~ 6.5 after several major mergers is able to reproduce a number of observed properties of SDSS J1148+5251, the most distant quasar detected at z = 6.42 (Fan et al. 2003). Moreover, the SMBHs grow through gas accretion below the Eddington limit in a self-regulated manner owing to feedback. We find that the progenitors experience vigorous star formation (up to 104 M? yr-1) preceding the major quasar phase such that the stellar mass of the quasar host reaches 1012 M? at z ~ 6.5, consistent with observations of significant metal enrichment in SDSS J1148+5251. The merger remnant thus obeys a similar MBH-Mbulge scaling relation observed locally as a consequence of coeval growth and evolution of the SMBH and its host galaxy. Our results provide a viable formation mechanism for z ~ 6 quasars in the standard ?CDM cosmology and demonstrate a common, merger-driven origin for the rarest quasars and the fundamental MBH-Mbulge correlation in a hierarchical universe.

The mass distribution in early-type disc galaxies: declining rotation curves and correlations with optical properties

We present rotation curves for 19 early-type disc galaxies (S0-Sab). The galaxies span a B-band absolute magnitude range from -17.5 to -22, but the majority have a high luminosity with M-B <-20. Rotation velocities are measured from a combination of H I velocity fields and long-slit optical emission line spectra along the major axis; the resulting rotation curves probe the gravitational potential on scales ranging from 100 pc to 100 kpc. We find that the rotation curves generally rise rapidly in the central regions and often reach rotation velocities of 200-300 km s(-1) within a few hundred parsecs of the centre. The detailed shape of the central rotation curves shows a clear dependence on the concentration of the stellar light distribution and the bulge-to-disc luminosity ratio: galaxies with highly concentrated stellar light distributions reach the maximum in their rotation curves at relatively smaller radii than galaxies with small bulges and a relatively diffuse light distribution. We interpret this as a strong indication that the dynamics in the central regions are dominated by the stellar mass. At intermediate radii, many rotation curves decline, with the asymptotic rotation velocity typically 10-20 per cent lower than the maximum. The strength of the decline is correlated with the total luminosity of the galaxies, more luminous galaxies having on average more strongly declining rotation curves. At large radii, however, all declining rotation curves flatten out, indicating that substantial amounts of dark matter must be present in these galaxies too. A comparison of our rotation curves with the Universal Rotation Curve from Persic et al. reveals large discrepancies between the observed and predicted rotation curves; we argue that rotation curves form a multiparameter family which is too complex to describe with a simple formula depending on total luminosity only. In a number of galaxies from our sample, there is evidence for the presence of rapidly rotating gas in the inner few hundred parsecs from the centres. The inferred central masses and mass densities are too high to be explained by the observed stellar components and suggest the presence of supermassive black holes in these galaxies.

Suppression of star formation in early-type galaxies by feedback from supermassive black holes

Detailed high-resolution observations of the innermost regions of nearby galaxies have revealed the presence of supermassive black holes. These black holes may interact with their host galaxies by means of 'feedback' in the form of energy and material jets; this feedback affects the evolution of the host and gives rise to observed relations between the black hole and the host. Here we report observations of the ultraviolet emissions of massive early-type galaxies. We derive an empirical relation for a critical black-hole mass (as a function of velocity dispersion) above which the outflows from these black holes suppress star formation in their hosts by heating and expelling all available cold gas. Supermassive black holes are negligible in mass compared to their hosts but nevertheless seem to play a critical role in the star formation history of galaxies.

Feedback Limits Rapid Growth of Seed Black Holes at High Redshift

Seed black holes formed in the collapse of Population III stars have been invoked to explain the presence of supermassive black holes at high redshift. It has been suggested that a seed black hole can grow up to through highly super-Eddington accretion for a period of similar to 10(6)-10(7) at redshift. We studied the feedback of radiation pressure, Compton heating, and outflow during the seed black hole growth. It is found that its surrounding medium fueled to the seed hole is greatly heated by Compton heating. For a supercritical accretion onto a seed hole, a Compton sphere ( with a temperature similar to 10(6) K) will be formed 10(3) M-circle dot on a timescale of 1.6 x 10(3) yr so that the hole is only supplied by a rate of 10(-3) of the Eddington the Compton sphere. The kinetic feedback of the strong outflow will heat the medium at a large distance from the black hole; this leads to a dramatic decrease of the outer Bondi accretion onto the black hole and avoids the accumulation of the matter. The highly supercritical accretion will be rapidly halted by the strong feedback. The seed black hole hardly grows up at the very early universe unless the strong feedback can be avoided.