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TOPIC: Supermassive Black Holes
Blobrana


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Nearby Supermassive Black Holes
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Title: Masses of Nearby Supermassive Black Holes with Very-Long Baseline Interferometry
Authors: Tim Johannsen, Dimitrios Psaltis (Arizona), Stefan Gillessen (MPE), Daniel P. Marrone, Feryal Ozel (Arizona), Sheperd S. Doeleman, Vincent L. Fish (MIT Haystack)

Dynamical mass measurements to date have allowed determinations of the mass M and the distance D of the galactic center black hole Sgr A* as well as those of other nearby supermassive black holes. In the case of Sgr A*, these measurements are limited by a degeneracy between the mass and distance scaling roughly as M ~ D^2. Future very-long baseline interferometric observations will image a bright and narrow ring surrounding the shadow of the supermassive black hole, if its accretion flow is optically thin. In this paper, we show that the combination of dynamical measurements and VLBI imaging of the ring of Sgr A* breaks the degeneracy between mass and distance. We estimate the signal to noise ratio of near-future VLBI arrays consisting of five to six stations and simulate measurements of the mass and distance of Sgr A* using the expected size of the ring image and existing data of stellar ephemerides. We demonstrate that VLBI observations at 1 mm can already improve the error on the mass by a factor of three compared to the results from the monitoring of stellar orbits alone; observations at 0.5 mm can reduce the error by as much as a factor of 7.5. In addition, we calculate the angular sizes of the bright rings of a number of other nearby supermassive black holes and identify the optimal targets besides Sgr A* that could be imaged by a ground-based VLBI array or a future space-VLBI mission allowing for refined mass measurements.

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Blobrana


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RE: Supermassive Black Holes
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Title: Feeding compact bulges and supermassive black holes with low angular-momentum cosmic gas at high redshift
Authors: Yohan Dubois, Christophe Pichon, Martin Haehnelt, Taysun Kimm, Adrianne Slyz, Julien Devriendt, Dmitry Pogosyan

We use cosmological hydrodynamical simulations to show that a significant fraction of the gas in high redshift rare massive halos falls nearly radially to their very centre on extremely short timescales. This process results in the formation of very compact bulges with specific angular momentum a factor 5-30 smaller than the average angular momentum of the baryons in the whole halo. Such low angular momentum originates both from segregation and effective cancellation when the gas flows to the centre of the halo along well defined cold filamentary streams. These filaments penetrate deep inside the halo and connect to the bulge from multiple rapidly changing directions. Structures falling in along the filaments (satellite galaxies) or formed by gravitational instabilities triggered by the inflow (star clusters) further reduce the angular momentum of the gas in the bulge. Finally, the fraction of gas radially falling to the centre appears to increase with the mass of the halo; we argue that this is most likely due to an enhanced cancellation of angular momentum in rarer halos which are fed by more isotropically distributed cold streams. Such an increasingly efficient funnelling of low-angular momentum gas to the centre of very massive halos at high redshift may account for the rapid pace at which the most massive supermassive black holes grow to reach observed masses around 10^9 solar masses at an epoch when the Universe is barely 1 Gyr old.

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Blobrana


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GigaPan Time Machine Aids Discovery About Black Holes

Researchers at Carnegie Mellon University's Bruce and Astrid McWilliams Centre for Cosmology have discovered what caused the rapid growth of early supermassive black holes - a steady diet of cold, fast food.
Computer simulations, completed using supercomputers at the National Institute for Computational Sciences and the Pittsburgh Supercomputing Centre, and viewed using CMU's GigaPan technology, show that thin streams of cold gas flow uncontrolled into the center of the first black holes, causing them to grow faster than anything else in the universe. The findings will be published in the Astrophysical Journal Letters.
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Where Have All the Quasars Gone?

An international team of astronomers has discovered two gigantic black holes with masses about 10 billion times the mass of our sun. These black holes have a mass more than 50 per cent greater than any other previously measured.
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Two biggest black holes ever found

Two huge black holes may be the largest yet measured. Supermassive black holes inhabit most large galaxies. One, in the galaxy Messier 87, has the mass of about 6 billion suns - but it is no longer the record holder.
There's one in galaxy NGC 3842 with the mass of about 10 billion suns, and NGC 4889's could weigh up to 37 billion suns, say Nicholas McConnell at the University of California, Berkeley, and colleagues.
The estimates were made by clocking the motion of stars near these galaxies' cores, since a black hole's mass dictates how fast objects orbit around them.
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Title: Two Nearby 10-Billion Solar Mass Black Holes
Authors: Nicholas J. McConnell, Chung-Pei Ma, Karl Gebhardt, Shelley A. Wright, Jeremy D. Murphy, Tod R. Lauer, James R. Graham and Douglas O. Richstone

Observational work conducted over the last few decades indicates that all massive galaxies harbour supermassive black holes at their centers. Although the luminosities and brightness fluctuations of quasars in the early Universe suggest that some are powered by black holes containing more than 10 billion solar masses, the remnants of these objects have not been found in the nearby Universe. For over three decades, the giant elliptical galaxy Messier 87 has hosted the most massive known black hole, with a mass of 6.3 billion solar masses. Here we report the discovery of a 9.7 billion solar mass black hole in NGC 3842, a brightest cluster galaxy at the center of a galaxy cluster 321 million light years away, and a black hole of comparable or larger mass in NGC 4889, the brightest galaxy in the Coma cluster 336 million light years away. The black holes in NGC 3842 and NGC 4889 are significantly more massive than predicted by linearly extrapolating the widely-used correlations between black hole mass and stellar velocity dispersion or bulge luminosity of the host galaxy. While these correlations remain useful for less massive elliptical galaxies, our new measurements suggest that different evolutionary processes influence the growth of the largest galaxies and their black holes.

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Record massive black holes discovered lurking in monster galaxies

University of California, Berkeley, astronomers have discovered the largest black holes to date - two monsters with masses equivalent to 10 billion suns that are threatening to consume anything, even light, within a region five times the size of our solar system.
These black holes are at the centers of two galaxies more than 300 million light years from Earth, and may be the dark remnants of some of the very bright galaxies, called quasars, that populated the early universe.
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Black holes surrounded by 'dust clouds'

Fat doughnut-shaped dust shrouds that obscure about half of supermassive black holes could be the result of high speed crashes between planets and asteroids, according to a new theory from an international team of astronomers.
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Planets smashed into dust near supermassive black holes

Fat doughnut-shaped dust shrouds that obscure about half of supermassive black holes could be the result of high speed crashes between planets and asteroids, according to a new theory from an international team of astronomers. The scientists, led by Dr. Sergei Nayakshin of the University of Leicester, publish their results in the journal Monthly Notices of the Royal Astronomical Society.
Supermassive black holes reside in the central parts of most galaxies. Observations indicate that about 50% of them are hidden from view by mysterious clouds of dust, the origin of which is not completely understood. The new theory is inspired by our own Solar System, where the so-called zodiacal dust is known to originate from collisions between solid bodies such as asteroids and comets. The scientists propose that the central regions of galaxies contain not only black holes and stars but also planets and asteroids.
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Force-fed black holes grew to master early universe

Black holes have to suck in matter to grow. That takes time, yet somehow the early universe contained supermassive black holes, hundreds of thousands of times larger than our sun.
The puzzle of how they got there when the universe was still so young lies in the Eddington rate - the name for the upper speed limit at which black holes can gather mass. All objects unfortunate enough to get caught in a black hole's eddyMovie Camera give off radiation as they spiral toward the abyss. At a certain point, the energy they give off will equal the black hole's pulling power and this sets a maximum limit on the rate at which matter can be sucked in.
Now Cole Miller, an astrophysicist from the University of Maryland, suggests that a funnel effect accelerated black hole development.
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