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Collective X-ray emission from distant galaxies reveals a hidden population of supermassive black holes. This finding suggests that galaxies and their central black holes have been coevolving since early cosmic times. See Letter p.356 A study of archival X-ray data from the Chandra X-ray observatory provides a measure of black hole growth at the earliest epochs at which observations are possible, around 600 million years after the Big Bang, at a redshift of z = 6–8. The results imply that black holes grow in tandem with their host galaxies, starting from the earliest times. The most copiously accreting black holes are buried in significant amounts of gas and dust that absorb most radiation except for the highest energy X-rays, and do not contribute to the re-ionization of the Universe.

Along with the presently believed black holes that are expected to be formed by gravitational collapse of massive star, there may exist primordial very hot evolving black holes and their origin may be interlinked with the Planck mass. Extending this proposal, the current universe can be considered as a huge evolving black hole of radius equal to the current Hubble length and temperature equal to 2.725 K. It can be suggested that 1) Vacuum is a great reservoir for matter and energy. 2) Planck mass can be considered as the primordial very hot baby black hole and can be called as the baby Planckion. 3) Baby Planckion will grow by absorbing the vacuum energy and thereby its geometric horizon also increases. As the baby Planckion is growing, its temperature and the tendency of vacuum energy absorption will decrease. 4) Very high temperature of the baby Planckion is the heat source for the evolving Planckion’s decreasing temperature. 5) Growing Planckion can be considered as the seed and center of any galaxy. 6) Growing Planckion will permit the emission of radiation. 6) Current universe can be considered as a huge evolving Planckion with temperature 2.725 K. In support this proposal, it is possible to guess that, in the past decreasing comic black whole temperature forced hydrogen atom to emit increased quantum of energy resulting in the observed redshift.

Ask an astronomer to name a theorist who observes, or vice versa, and Doug Richstone's name is sure to come up. Doug's first flirtations with astronomy resulted from a childhood fascination with the colors of stars in Orion. Despite a bicoastal education at Caltech and Princeton, he flourishes in the midwest as Professor of Astronomy at the University of Michigan. Doug is fond of saying that a busy research and teaching schedule, and too many committee trips, leave him little time for reading, hiking, and recreational travel. Despite this, he has accomplished something wonderful for this book: a fascinating essay describing the slow but nevertheless dramatic revolution in thinking about massive black holes and their role in the evolution of galaxies. In this essay Doug combines two of his career-long fascinations—the dynamics of stars and the nature of quasars—with his enjoyment of team play, to explore the black holes that lie at the center of so many galaxies. When Alan Dressler called me in 1984, massive black holes were not on my agenda. I had known Alan since the mid-seventies when we were postdoctoral fellows, he at the Carnegie Observatories, I at Caltech. Although we hadn't worked together, his thesis, which included great observational work on clusters of galaxies, was very germane to the theoretical work I had done in my thesis, so I thought he chose good problems and did them well.

We show that cold dark matter (CDM) captured in the very first gravitationally bound objects formed in the early Universe has a velocity dispersion small enough to allow individual stars to retain a significant amount of CDM in their interior. If CDM comprises primordial black holes (PBHs) as a minor component, this could have a dramatic effect on the fate of such stars even if PBHs constitute only 10−9−10−8 fraction of the critical density of the Universe, which is consistent with the non-detection of hard gamma-ray emission from evaporating black holes.

The means by which supermassive black holes form and grow have remained largely unclear. Numerical simulations show that the collision of massive galaxies can naturally lead to the creation of these objects.

Recently Pen and Spergel (1997) have shown that a universe whose energy density is dominated by a frustrated network of non-Abelian TeV-scale cosmic strings could account for a broad class of cosmological observations. In this paper we consider the effects of such a string network on the massive black holes widely believed to inhabit the centers of many galaxies. As these black holes traverse the universe together with their host galaxies, they would intersect a large number of string segments. We argue that such segments would become stuck to the black hole, and be stretched by the hole's motion. Stretching the strings would cause significant deceleration of the black holes. Although the black holes would probably not be removed from the galaxies completely, they would be noticeably displaced from the galactic center of mass -- by at least 5kpc. This displacement seems to be is contradiction to the observational evidence., 9 pages, 2 figures, accepted for publication in Phys. Rev.D

There is only indirect evidence of the existence of black holes. A laboratory demonstration of an X-ray interferometer is a step towards achieving the angular resolution necessary to obtain a direct, X-ray image of a black hole.

This review addresses one of the important topics of current astrophysical research, namely the role that supermassive black holes play in shaping the morphology of their host galaxies. There is increasing evidence for the presence of massive black holes at the centers of all galaxies and many efforts are directed at understanding the processes that lead to their formation, the duty cycle for the active phase and the question of the fueling mechanism. Related issues are the epoch of formation of the supermassive black holes, their time evolution and growth and the role they play in the early ionization of the Universe. Considerable observational and theoretical work has been carried out in this field over the last few years and I will review some of the recent key areas of progress.

The observed growth of galaxies suggests that the black holes thought to lurk at their centres may find each other and merge. A large survey of galaxies has finally netted two black holes in a tight pairing.

IF black holes exist in the contracting phase of a closed universe, they will give rise to a pressure and entropy catastrophe. First, the black holes absorb all the radiation; then their apparent horizons merge, and coalesce with the cosmological apparent horizon. All external observers become internal observers. It is possible that the internal metric of some of the merging black holes will be contracting, and others expanding. I suggest here that the resulting violent inhomogeneities can lead to a reexpansion in a significant portion of the universe. Global reexpansion, prompted by the merging of black holes, may thus begin in a semi-classical rather than fully quantum gravitational era, at densities greater than those at which nucleosynthesis occurs. Surviving black holes and inhomogeneities could initiate the formation of structures such as galaxies in the 'new' universe. The behaviour of such an oscillating universe would differ in detail from cycle to cycle.

Astronomers have identified potential black holes in a variety of astrophysical objects. In binary star systems, consisting of two stars revolving around each other under the influence of their mutual gravitational attraction, black holes with masses of order several solar masses (M ~ 5 – 20M⊙) are thought to exist as the dead remnant of the initially more massive of the two stars.

We investigate the tidal disruption of a red giant whose envelope is thought to be stripped off when it passed by a massive black hole. Since the low-density stellar envelope would be lost, the tidal disruption of a red giant by massive black hole is regarded as primarily happening in its core region. The object is called a stripped red giant (SRG). Comparing our results with the three candidate tidal disruption events detected by Chandra in 2001 and 2002, i.e., the X-ray flares of NGC 5905, RX J1242.6-1119A, and RX J1624.9+7554, we argue that the tidal disruption of a stripped red giant is strongly ruled out.

The gravitational radiation emitted during the final stages of coalescence of stellar mass compact objects with low mass massive black holes is a signal that may be detected by LISA with some confidence, while also offering the possibility of measuring strong field effects in relativity. I consider the uncertainties in estimating the rate of such events, and the possibility of enhanced coalescence rates of low mass black holes with low mass massive black holes due to ongoing star formation in centers of galaxies. I also conjecture that x-ray precursors to coalescence may conceivably be observable in some cases.

The black hole phenomenon is undoubtedly one of the most striking and intriguing of those predicted by theorists. However, a paramount question is: “Do black holes exist in the Universe, or are they only an abstract concept of the human mind?” In principle, a black hole could be built artificially. However, this meets such grandiose technical difficulties that it looks impossible, at least in the immediate future. In fact, the artificial construction of a black hole looks even more problematic than an artificial creation of a star. Thus, we have to conclude that the physics of black holes, as well as the physics of stars, is the physics of celestial bodies. Stars definitely exist, but what may one say about the existence of astrophysical black holes?

When a star approaches the neighborhood of a supermassive black hole, the tidal forces acting on the star trigger a vast range of physical effects that could yield unique observational signatures. Of particular interest are ultraclose passages of stars by massive black holes. These encounters could not only unveil general relativistic effects but also provide favorable conditions for the detonation of the star. This article presents a general review of the tidal stellar disruption phenomenon.

The interaction of stars with a massive black hole probably plays an important role in physical processes in the central regions of QSOs and active galactic nuclei (AGNs), and even in global clusters and in the centers of normal g galaxies. (For review see [1], [2], [3], [4] and references therein).

We show, performing a viable cosmological window, that only the magneto hydrodynamic (MHD) disk model is capable to explain how an intermediate mass black hole (IMBH) (with masses ∼ 103M⊙) grows unto a supermassive black hole (SMBH) (with masses ∼ 107M⊙). We still calculate the supermassive stars sequence of stability. Those stars, with synthetized helium or oxygen cores, collapse to form IMBHs. In our calculation we show that the primordial stars must have rapid rotation if they are in the stable part of the sequence.

ASTROPHYSICSBlack holes may be harder to create than previously believed, according to an unexpected discovery made with NASA's Chandra X-ray Observatory.

Supermassive stars and quasi-stars (massive stars with a central black hole) are both considered as potential progenitors for the formation of supermassive black holes. They are expected to form from rapidly accreting protostars in massive primordial halos. We explore how long rapidly accreting protostars remain on the Hayashi track, implying large protostellar radii and weak accretion luminosity feedback. We assess the potential role of energy production in the nuclear core, and determine what regulates the evolution of such protostars into quasi-stars or supermassive stars. We follow the contraction of characteristic mass scales in rapidly accreting protostars, and infer the timescales for them to reach nuclear densities. We compare the characteristic timescales for nuclear burning with those for which the extended protostellar envelope can be maintained. We find that the extended envelope can be maintained up to protostellar masses of 3.6x10^8 \dot{m}^3 solar, where \dot{m} denotes the accretion rate in solar masses per year. We expect the nuclear core to exhaust its hydrogen content in 7x10^6 yrs. If accretion rates \dot{m}>>0.14 can still be maintained at this point, a black hole may form within the accreting envelope, leading to a quasi-star. Alternatively, the accreting object will gravitationally contract to become a main-sequence supermassive star. Due to the limited gas reservoir in dark matter halos with 10^7 solar masses, the accretion rate onto the central object may drop at late times, implying the formation of supermassive stars as the typical outcome of direct collapse. However, if high accretion rates are maintained, a quasi-star with an interior black hole may form., 9 pages, 4 figures, submitted to A&A. Comments are welcome

Our numerical tool is SUPERBOX (Bien et al., 1991) which can treat an arbitrary number of galaxies. Simulations including Black Holes are important to understand recent observations, see e. g. Mediavilla and Arribas (1993).

Can we determine spin parameters of black holes by observations of black hole shadows in accretion disks? In order to answer this question, we have investigated shapes and positions of black hole shadows in optically thick accretion disks around Kerr black holes. In conclusion, in order to measure black hole spin parameters from shapes and positions of black hole shadows, it is crucially important to determine a position of a mass centers of a black hole in a region of a black hole shadow. To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Quasars, the oldest known objects in the Universe, are powered by gas falling into black holes at their centres. How black holes formed so early in time has been hard to explain, but a new model might have the answer.

We present results of numerical simulations of mergers of spiral galaxies using GADGET (Springel, Yoshida, & White 2001). In three of these simulations one of the progenitor galaxies contained a central supermassive black hole (BH), as well as one simulation which did not contain a BH. The merger remnants were evolved to an age of ∼ 13 Gyr to examine the evolution of the shape of each merger remnant. The results of these simulations were compared to observations of elliptical galaxies, which show that older galaxies appear rounder than younger ones (Ryden, Forbes, & Terlevich 2001).We found that the simulations in which the BH mass was fixed throughout the evolution influence the shape of their host galaxies on timescales less than 3 Gyr. These simulations show little trend of shape with age beyond this time. In the simulations in which the BH mass increased linearly over the duration of the simulation, there is a significant evolution of the shape of the remnant throughout its lifetime, comparable to the observational trend.

When a star wanders too close to a giant black hole, it can be pulled apart by the black hole's tidal force. One such event offers insight into the properties of both the black hole and the star. Central supermassive black holes in distant galaxies are normally invisible to us, but sometimes their presence becomes evident in the form of flares produced by the tidal disruption of a star being accreted to the black hole. Such events are rare, and often we see only the later stages of the encounter — but here, Gezari et al. report detailed monitoring of an ultraviolet and optical flare from the nuclear region of an inactive galaxy at a redshift of 0.1696, which was first seen on 31 May 2010, peaked in July and was over by September. The observed continuum is cooler than expected for a simple accreting debris disk, but the well sampled rise and decline of the light curve follows the predicted mass-accretion rate. The black hole has about two million solar masses and the disrupted star had a helium-rich stellar core, as the authors deduced from the spectroscopic signature of ionized helium from the unbound debris.

A star with main sequence mass greater than $25\sim 30\msun$ may collapse to a black hole of about 10 $\msun$ at the final stage of the evolution. About an order of 1\% of stellar mass is likely to be in form of such black holes in galaxies. We have examined the dynamics of two-component stellar systems composed of 0.7 $\msun$ main-sequence stars, representing the old population of stars whose main-sequence lifetimes are longer than the Hubble time, and a small fraction of 10 $\msun$ black holes. The dynamical friction leads to the segregation of black holes to the core and the core collapse takes place among the black holes in a time scale much shorter than that required for a single component cluster. The ultimate evolution of the two-component stellar system depends on the role of three-body binaries formed among the black holes. For a system with $v\gta 100\kms$ binaries merge by gravitational radiation at some hardness instead of being ejected. The critical hardness, at which the collision time and the merger time become comparable, determines the efficiency of the binary as a heat source. The efficiency is found to be inversely proportional to the velocity dispersion. For the clusters without serious reduction in heating efficiency (i.e., velocity dispersion well below 500 $\kms$), heating by three-body binaries have the effect of stopping the core-collapse. The cluster, 25 pages; uuencoded compressed postscript including 5 figures; to appear in MNRAS

Supermassive black holes are investigated as possible sources for low-frequency bursts of gravity waves. The event rate for `known' supermassive black holes at intermediate and high redshifts, inferred from the quasar luminosity function, is low $\sim 0.1 \yr^{-1}$. A space-based interferometer could therefore only see several events per year from supermassive black holes if an additional population of supermassive black holes existed and emitted gravitational waves efficiently. These might reside in the population of dwarf galaxies or in a transient population of small dark matter haloes that have mostly merged into larger haloes hosting the galaxies seen today. The proposed space-based gravitational-wave interferometer LISA/SAGITTARIUS should detect most gravitational-wave events involving supermassive black holes above $10^{4} \Msol$ out to redshifts of $z \sim 100$., Comment: 18 pages (including 5 Figures), uuencoded postscript file

The tidal disruption of a star by a massive Schwarzschild black hole and subsequent evolution of stellar debris is followed numerically using Smoothed Particle Hydrodynamics (SPH). After the disruption of the star, the gaseous particles are distributed evenly in energy space which is translated to a period distribution of N(P)dP ∝ P- 5/3. Half the stellar debris is found to have positive binding energy so that only half of the stellar material will move along bound orbits. The orbits of particles in relativistic gravitational potential are calculated using the post-Newtonian approximation up to the order of υ2 /c 2. The stream of incoming particles with short orbital periods intersect with the outgoing stream of particles with long orbital periods because of relativistic precession, producing strong hydrodynamic shocks. Such a shock transforms orbital energy to thermal energy. This process circularizes the orbits of particles. Our calculations clearly show the early phase of circularization from which we may be able to predict the later evolution.

How did black holes grow so big so fast in the early universe? New calculations bolster the case that they formed in the bellies of gaseous cocoons

A mysterious disc at the heart of the Andromeda galaxy may explain how supermassive black holes ate enough material to bulk up to their huge sizes

ROCHESTER, NEW YORK-- The origin of massive black holes and the galaxies that surround them is a chicken-and-egg conundrum. Now, researchers reported here last week at a meeting of the American Astronomical Society that giant black holes and their host galaxies appear to be cosmic siblings that grew up at the same time. That conclusion rests on a newly unveiled relationship between the masses of black holes and how tightly gravity binds together the billions of stars around them.

American Astronomical Society 214th Meeting, 7–11 June 2009, Pasadena, CaliforniaDistant quasars harbor at their centers black holes as massive as 10 billion suns. The black holes in the middle of nearby galaxies are featherweights by comparison. Why the difference? According to new research presented at the American Astronomical Society meeting, astronomers may have been systematically underestimating nearby black hole masses by a factor of two to three. The finding is likely to make astrophysicists rethink how galaxies form around black holes.

Fresh observations suggest that the rotation of black holes provides the power for devastating jets that rip through surrounding galaxies

The digested end-product could be the ancestors of the supermassive black holes that sit at the centre of galaxies like the Milky Way

Primordial black holes may have radiated gamma rays that lit up the universe long before the first stars were born

Most of the talks at this conference deal with dark matter in the outlying parts of galaxies. This paper, in contrast, discusses the dark objects, probably massive black holes, which lurk at the centres of such normal galaxies as M31, and perhaps even our own. This subject is approached historically by considering the cosmic history of the quasar population. The evidence for massive black holes in the centres of some nearby galaxies is reviewed. Some interesting observational consequences (eg flares from tidally disrupted stars) are proposed and discussed.

A black hole 16 times the mass of the sun could provide a clue to the formation of the supermassive black holes in galaxy centres

Primordial non-linear structures appear in inflationary Universe as natural reflection of particle symmetry on super high energy scale. Large scale correlations in the energy density distribution of coherent axion field oscillations (archioles), primordial clouds of massive Black holes and antimatter stars in baryon asymmetrical Universe represent examples of such structures, being the challenge for experimental methods of precision cosmology.

We discuss the formation of stellar mass black holes via protoneutron star (PNS) collapse. Such PNSs are modelled as central objects in general relativistic ID core collapse simulations with Boltzmann neutrino transport. In the absence of an earlier explosion, the PNS collapses eventually due to continued accretion of outer layers of a massive star onto the central object. We investigate the resulting conditions with respect to neutrino emission at the formation of a black hole.

A group of galaxies emits strong permitted and forbidden lines from the central part where a massive black hole is supposed to be located. The cores of this type of galaxies, so called Active Galactic Nuclei (AGN) are known as a most powerful sources of radiation in the Universe. Here we discuss the emitting plasma conditions in emitting line regions of AGN as well as methods which are in usage to determine the physical properties of the emitting plasma around super massive black holes.

In the Autumn of 1991, Nakai et al.(1993) began monitoring observations of water mega masers including NGC4258 using Nobeyama 45 m telescope. The 45 m telescope was equipped with wide band cooled HEMT receiver (22 GHz) and wide band spectrometers (AOS). Nakai used 8 AOSs which covered 4480 km/sec in velocity. It was from the wide-band system that the high velocity maser components were detected unexpectedly which locate ±1000 km/sec from the known features of the NGC4258 (Claussen et al. 1984). The finding was in May 1992 when busy Nakai got time checking the data deeply, half year had passed since the beginning of the observations.

We review the topic of jets in the universe, starting with the early history. We focus on jets from X-ray binaries, discussing the constrasts between the jets seen from black holes and from neutron stars. We then show the implications of results on X-ray binaries for studies of active galactic nuclei, and other black holes not in binary systems, such as stellar-mass black holes accreting from molecular clouds, and intermediate-mass black holes accreting from the interstellar medium in globular clusters. We close by listing some open issues on the topic.