* Astronomy

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RE: Massive black holes

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Title: An origin of the radio jet in M87 at the location of the central black hole
Authors: Kazuhiro Hada, Akihiro Doi, Motoki Kino, Hiroshi Nagai, Yoshiaki Hagiwara & Noriyuki Kawaguchi

Powerful radio jets from active galactic nuclei are thought to be powered by the accretion of material onto the supermassive black hole (the 'central engine'). M87 is one of the closest examples of this phenomenon, and the structure of its jet has been probed on a scale of about 100 Schwarzschild radii (Rs, the radius of the event horizon). However, the location of the central black hole relative to the jet base (a bright compact radio 'core') remains elusive. Observations of other jets indicate that the central engines are located about 10^4 - 10^6Rs upstream from the radio core. Here we report radio observations of M87 at six frequencies that allow us to achieve a positional accuracy of about 20 microarcseconds. As the jet base becomes more transparent at higher frequencies, the multifrequency position measurements of the radio core enable us to determine the upstream end of the jet. The data reveal that the central engine of M87 is located within 14-23Rs of the radio core at 43 GHz. This implies that the site of material infall onto the black hole and the eventual origin of the jet reside in the bright compact region seen on the image at 43 GHz.

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Black hole exposed by radio emissions

A black hole 'unmasked' by the strong radio emission: for the first time, astrophysicists have been able to point their telescopes on the mysterious object. The results are published in Nature by the research group of the Graduate University for Advanced Studies in Tokyo, led by Kazuhiro Hada. The observations have allowed us to discover that the source of the radio emitting jets originate nearer the black hole than expected.
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Chandra Sheds Light on Black Holes

A NASA-hosted news conference in Washington highlights imagery and data captured by the Chandra X-Ray Observatory about the early universe's growth of supermassive black holes in galaxies.

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NASA'S Chandra Finds Massive Black Holes Common In Early Universe

Using the deepest X-ray image ever taken, astronomers found the first direct evidence that massive black holes were common in the early universe. This discovery from NASA's Chandra X-ray Observatory shows that very young black holes grew more aggressively than previously thought, in tandem with the growth of their host galaxies.
By pointing Chandra at a patch of sky for more than six weeks, astronomers obtained what is known as the Chandra Deep Field South (CDFS). When combined with very deep optical and infrared images from NASA's Hubble Space Telescope, the new Chandra data allowed astronomers to search for black holes in 200 distant galaxies, from when the universe was between about 800 million to 950 million years old.
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NASA to unravel new discovery about giant black holes on June 15

On Wednesday, June 15, NASA will announce a new discovery about giant black holes in the early universe.
This discovery was made using the Chandra X-ray Observatory. Chandra gives astronomers a powerful tool to investigate the universe, especially those hot spots where black holes, exploding stars and colliding galaxies are most likely to live.
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Astrophysicists use X-ray fingerprints to study eating habits of giant black holes

Georgia Tech astrophysicists have provided an important test of a long-standing theory that describes the extreme physics occurring when matter spirals into massive objects known as black holes.

By studying the X-rays emitted when superheated gases plunge into distant and massive black holes, astrophysicists at the Georgia Institute of Technology have provided an important test of a long-standing theory that describes the extreme physics occurring when matter spirals into these massive objects.
Matter falling into black holes emits tremendous amounts of energy which can escape as visible light, ultraviolet light and X-rays. This energy can also drive outflows of gas and dust far from the black hole, affecting the growth and evolution of galaxies containing the black holes. Understanding the complex processes that occur in these active galactic nuclei is vital to theories describing the formation of galaxies such as the Milky Way, and is therefore the subject of intense research.

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Title: Massive black holes lurking in Milky Way satellites
Authors: S. Van Wassenhove, M. Volonteri, M.G. Walker, J.R. Gair

As massive black holes (MBHs) grow from lower-mass seeds, it is natural to expect that a leftover population of progenitor MBHs should also exist in the present universe. Dwarf galaxies undergo a quiet merger history, and as a result, we expect that dwarfs observed in the local Universe retain some 'memory' of the original seed mass distribution. Consequently, the properties of MBHs in nearby dwarf galaxies may provide clean indicators of the efficiency of MBH formation. In order to examine the properties of MBHs in dwarf galaxies, we evolve different MBH populations within a Milky Way halo from high-redshift to today. We consider two plausible MBH formation mechanisms: 'massive seeds' formed via gas-dynamical instabilities and a Population III remnant seed model. 'Massive seeds' have larger masses than PopIII remnants, but form in rarer hosts. We dynamically evolve all halos merging with the central system, taking into consideration how the interaction modifies the satellites, stripping their outer mass layers. We compute different properties of the MBH population hosted in these satellites. We find that for the most part MBHs retain the original mass, thus providing a clear indication of what the properties of the seeds were. We derive the black hole occupation fraction (BHOF) of the satellite population at z=0. MBHs generated as 'massive seeds' have large masses that would favour their identification, but their typical BHOF is always below 40 per cent and decreases to less than per cent for observed dwarf galaxy sizes. In contrast, Population III remnants have a higher BHOF, but their masses have not grown much since formation, inhibiting their detection.

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