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Re-send: NASA's Chandra Finds Evidence for Quasar Ignition (correct vers

Subject: Re-send: NASA's Chandra Finds Evidence for Quasar Ignition correct version
From: Andrew Yee <""ayee \"@ nova.astro.utoronto.ca">
Date: Thu, 23 Mar 2006 13:37:10 -0500
Newsgroups: sci.astro
Due to a mistake the news release posted here yesterday was an incorrect version. The correct version appears below.
*****

Steve Roy
Marshall Space Flight Center, Huntsville, Ala.        March 23, 2006
(Phone: 256/544-6535)

Megan Watzke
Chandra X-ray Center, Cambridge, Mass.
(Phone: 617/496-7998)

CXC release: 06-02

NASA's Chandra Finds Evidence for Quasar Ignition

New data from NASA's Chandra X-ray Observatory may provide clues to how quasars "turn on." Since the discovery of quasars over 40 years ago, astronomers have been trying to understand the conditions surrounding the birth of these immensely powerful objects.
Hot, X-ray producing regions around two distant quasars observed by
Chandra are thought to have formed during their activation. These
features are located tens of thousands of light years from the central
supermassive black holes thought to power the quasars.
"The X-ray features are likely shock waves that could be a direct result
of the turning on of the quasar about 4 billion years ago," said Alan
Stockton of the University of Hawaii in Honolulu, and lead author of a
report on this work published recently in The Astrophysical Journal.
The quasars, 4C37.43 and 3C249.1, showed no evidence for the existence
of a much larger envelope of hot gas around the features, nor were the
observed X-ray regions associated with radio waves from the quasars.
These factors rule out possible explanations for the X-ray emitting
clouds, such as the cooling of hot intergalactic gas, or heating by
high-energy jets from the quasars.
"The best explanation for our observations is that a burst of star
formation, or the activation of the quasar itself, is driving an
enormous amount of gas away from the quasar's host galaxy at extremely
high speeds," said Hai Fu, a coauthor of the study who is also from the
University of Hawaii.
Computer simulations of the formation of stars and the growth of black
holes during a collision between two galaxies are consistent with this
picture. The simulations, performed by Tiziana Di Matteo of
Carnegie-Mellon University in Pittsburgh, Pennsylvania, and colleagues,
show that the merger of galaxies drives gas toward the central regions
where it triggers a burst of star formation and provides fuel for the
growth of a central black hole.
The inflow of gas into the black hole releases a tremendous amount of
energy, and a quasar is born. The power output of the quasar dwarfs that
of the surrounding galaxy and expels gas from the galaxy in what has
been termed a galactic superwind. The Chandra data provide the best
evidence yet for a quasar-produced superwind.
Over a period of about 100 million years, the superwind will drive all
the gas away from the central regions of the galaxy, quenching both star
formation and further black hole growth. The quasar phase will end and
the galaxy will settle down to a relatively quiet life. The tranquility
of the galaxy will be interrupted from time to time as a small satellite
galaxy is captured and provides food for the otherwise dormant
supermassive black hole.
Other members of the research team were J. Patrick Henry, also of the
University of Hawaii, and Gabriela Canalizo of the University of
California, Riverside. NASA's Marshall Space Flight Center, Huntsville,
Ala., manages the Chandra program for the agency's Science Mission
Directorate. The Smithsonian Astrophysical Observatory provides science
support and controls flight operations from the Chandra X-ray Center in
Cambridge, Mass.
Additional information and images are available at:

     http://chandra.harvard.edu/photo/2006/4c37/
and
     http://www.nasa.gov/centers/marshall/news/chandra/

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