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Astronomers Discover Upper Limit for Mass of Giant Black Holes (Forwarded)



 
 
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Old September 15th 08, 05:49 PM posted to sci.space.news
Andrew Yee[_1_]
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Default Astronomers Discover Upper Limit for Mass of Giant Black Holes (Forwarded)

Institute for Astronomy
University of Hawaii at Manoa

Contacts:
Dr. Ezequiel Treister
Institute for Astronomy
University of Hawaii at Manoa
1-808-956-6664

Prof. Priya Natarajan
Yale University

Mrs. Karen Rehbock
Assistant to the Director
Institute for Astronomy
University of Hawaii at Manoa
1-808-956-6829

For immediate release: September 9, 2008

Astronomers Discover Upper Limit for Mass of Giant Black Holes

There appears to be an upper limit to how big the universe's most massive
black holes can get, according to new research by astrophysicists from the
University of Hawaii and Yale University. This limit is 10 billion times the
mass of the Sun or about one percent of the total mass of the giant galaxies
in which these black holes are found.

Once considered rare and exotic objects, black holes are now known to exist
throughout the universe, with the most massive found at the centers of the
largest galaxies. These "ultra-massive" black holes have been shown to have
masses upwards of one billion times that of our own Sun. Now, Ezequiel
Treister, a Chandra postdoctoral fellow at the University of Hawaii and
Priyamvada Natarajan, an associate professor of astronomy and physics at
Yale University, have shown that even the biggest of these gravitational
monsters can't keep growing forever. Instead, they appear to curb their own
growth -- once they accumulate about 10 billion times the mass of the Sun.

These ultra-massive black holes, found at the centers of giant elliptical
galaxies in huge galaxy clusters, are the biggest in the known universe.
Even the large black hole at the center of our own Milky Way galaxy is
thousands of times less massive than these behemoths. But these gigantic
black holes, which accumulate mass by sucking in matter from neighboring
gas, dust and stars, seem unable to grow beyond this limit regardless of
where -- and when -- they appear in the universe. "It's not just happening
today," said Natarajan. "They shut off at every epoch in the universe."

The study, to appear in the Monthly Notices of the Royal Astronomical
Society (MNRAS), represents the first time an upper mass limit has been
derived for black holes. Natarajan and Treister used existing optical and
X-ray data of these ultra-massive black holes to show that, in order for
those various observations to be consistent, the black holes must
essentially shut off at some point in their evolution. "Getting a complete
observational census of black holes from X-ray data, using the deepest
observations with the Chandra Observatory, was an important piece in this
puzzle," said Treister.

Several groups have suggested possible growth control mechanisms. One
possible explanation, derived by Natarajan in earlier work, is that the
black holes might eventually reach the point when they radiate so much
energy as they consume their surroundings that they end up interfering with
the very gas supply that feeds them, which may also interrupt star formation
in the vicinity. The new findings have implications for the future study of
galaxy formation, since many of the largest galaxies in the universe appear
to co-evolve along with the black holes at their centers.

"Evidence has been mounting for the key role that black holes play in the
process of galaxy formation," said Natarajan. "But it now appears that they
are likely the prima donnas of this space opera."

The authors of the paper are Priyamvada Natarajan (Yale University and the
Radcliffe Institute for Advanced Study) and Ezequiel Treister (Institute for
Astronomy, University of Hawaii).

Support for this work was provided by the National Aeronautics and Space
Administration through Chandra Postdoctoral Fellowship Award Number
PF8-90055 issued by the Chandra X-ray Observatory Center, which is operated
by the Smithsonian Astrophysical Observatory for and on behalf of the
National Aeronautics Space Administration under contract NAS8-03060.

The Hubble Space Telescope is operated by the Space Telescope Science
Institute with funding from NASA.

Founded in 1967, the Institute for Astronomy at the University of Hawaii at
Manoa conducts research into galaxies, cosmology, stars, planets, and the
sun. Its faculty and staff are also involved in astronomy education, deep
space missions, and in the development and management of the observatories
on Haleakala and Mauna Kea.

Established in 1907 and fully accredited by the Western Association of
Schools and Colleges, the University of Hawaii is the state's sole public
system of higher education. The UH System provides an array of
undergraduate, graduate, and professional degrees and community programs on
10 campuses and through educational, training, and research centers across
the state. UH enrolls more than 50,000 students from Hawaii, the U.S.
mainland, and around the world.

Related links:

* More info
http://www.sc.eso.org/~etreiste/UMBHs/more_info.html
* Paper preprint
http://arxiv.org/abs/0808.2813

IMAGE CAPTION:
[http://www.ifa.hawaii.edu/info/press...8/fig1_web.jpg
(78KB)]
Image of the giant elliptical galaxy ESO 325-G004 taken by the Hubble Space
Telescope using the Advanced Camera for Surveys. This giant galaxy, with a
mass of about 100 billion solar masses, is located in the center of the
galaxy cluster Abell S0740, 450 million light-years away from us in the
Centaurus constellation. Giant elliptical galaxies, typically found in the
centers of galaxy clusters, like ESO 325-G004 are the hosts of ultra-massive
black holes with masses larger than five billion solar masses. Credit: NASA,
ESA, and The Hubble Heritage Team (STScI/AURA). Acknowledgment: J. Blakeslee
(Washington State University)
 




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