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Topic Name: The precise locations and environments of a pair of supermassive black holes at the center of an ongoing collision between two galaxies 300 million light-years away
Category: Multi-mode multimedia (M4) technologies
Research persons: Dr. Claire E. Max, E. Gabriela Canalizo ,Willem de Vries,
Location: Center for Adaptive Optics, University of California,1156 High St,Santa Cruz CA 95064, United States
Details
Astronomers have used powerful adaptive optics technology at
the W. M. Keck Observatory in Hawaii to reveal the precise locations and
environments of a pair of supermassive black holes at the center of an ongoing
collision between two galaxies 300 million light-years away.The new observations
of the galaxy merger known as NGC 6240 reveal that each of the black holes
resides at the center of a rotating disk of stars and is surrounded by a cloud
of young star clusters formed in the merger, said Claire Max, professor of
astronomy and astrophysics at the University of California, Santa
Cruz."People had observed this pair of colliding galaxies at different
wavelengths and seen what they thought were the black holes, but it's been very
hard to make sense of how the observations at various wavelengths correspond to
each other," Max said. "The adaptive optics results enabled us to tie
it all together, so now we can really see it all--the hot dust in the infrared,
the stars in the visible and infrared, and the x-rays and radio emissions coming
from right around the black holes."
Adaptive
optics (AO) enables astronomers to counteract the blurring effects of turbulence
in Earth's atmosphere, which degrades images seen by ground-based
telescopes. Max, who directs the Center for Adaptive Optics at UC Santa
Cruz, is the lead author of a paper describing the new findings published by the
journal Science (Science Express online, May 17, and in a later print
edition). Her coauthors are Gabriela Canalizo, who worked with Max as a
postdoctoral researcher at Lawrence Livermore National Laboratory (LLNL) and is
now at UC Riverside, and Willem de Vries, a physicist with LLNL and UC Davis.
Images of NGC 6240 in visible light from the Hubble
Space Telescope show the outer parts of the colliding galaxies distorted by
their ongoing merger into long tidal tails of stars, gas, and dust. In the
bright central region, two distinct nuclei can be discerned, but clouds of dust
obscure much of the visible light from the core. The presence of two
supermassive black holes in NGC 6240 was first demonstrated by x-ray
observations from NASA's Chandra X-ray Observatory in 2002. Two point like radio
sources were also detected in the central region.
But trying to match up the data from one instrument with those
obtained at different wavelengths by other instruments is very difficult because
there are few common reference points in the various wavelength regimes, Max
said. The infrared images her group obtained using the AO system on the 10-meter
Keck II Telescope provided the high spatial resolution needed to identify
features in NGC 6240 that can be seen in different wavelengths.
"With the infrared images we got at Keck, we were able to
line up the information from all the different wavelengths to determine which
features in the images are the black holes," Max said.
The infrared wavelengths are less affected by dust than
visible light, and the Keck infrared images show distinct nuclei with complex
substructure surrounded by many faint point sources. The faint point sources are
young star clusters produced in a burst of star formation triggered by the
collision of the two gas-rich galaxies. Pinpointing which of the features in the
infrared images correspond to the positions of the black holes involved several
steps and required Keck adaptive optics observations at different infrared
wavelengths.
"We uncovered it piece by piece, until we were able to
make the correspondence between the black holes and the features seen at
different wavelengths, as well as the stuff around them," Max said.
"It really shows how powerful the Keck adaptive optics system is. We were
also fortunate to have an extraordinarily good observing night."
Galaxy mergers are thought to play a major role in the
evolution of galaxies and may help explain many of their properties. For
example, astronomers have found that the mass of the black hole at the center of
a galaxy is highly correlated with large-scale properties of the galaxy itself.
The "coevolution" hypothesis explains this correlation as the result
of both the black hole and the galaxy around it growing incrementally in
repeated merger events over cosmic timescales.
"The gravitational influence of the black hole is
actually limited to a relatively small region right around it, so how can it
affect the rest of the galaxy? But if the black hole and the galaxy around it
evolved together through the same sequence of merger events, that would explain
the correlations," Max said. "That's why people are so excited about
understanding galaxy mergers, and here we're seeing it in action."
The two black holes in NGC 6240 will eventually, in 10 million
to 100 million years, spiral into each other and merge, producing a powerful
burst of gravitational radiation, she said..
About Researchers:
Dr. Claire E. Max
Professor of Astronomy and Astrophysics
Astronomer, UC Observatories/ Lick Observatory
UC Santa Cruz
Other positions:
Director, Center for Adaptive Optics,
an NSF Science and Technology Center
Contact Information:
Office: Center for Adaptive Optics, Room 213
Phone: 831-459-2049, Fax: 831-459-5717
Email: max at ucolick.org
E. Gabriela Canalizo
Assistant Professor, Department of Earth Sciences Ph.D.
University of Hawaii (2000)
Ph: 951.827.5636
gabyc@ucr.edu
Willem de Vries,
Assistant Project Physicists
LLNL, IGPP L-413
(925)424-9775
Funded:
This research was supported in part by Lawrence Livermore
National Laboratory under the auspices of the U.S. Department of Energy and by
the Center for Adaptive Optics, a National Science Foundation Science and
Technology Center managed by UC Santa Cruz. The W. M. Keck Observatory is
operated as a scientific partnership among the California Institute of
Technology, the University of California, and NASA
In the Images :
NGC 6240 is an ongoing collision of two gas-rich disk
galaxies. Using adaptive optics at the Keck II Telescope, researchers have
resolved young star clusters formed because of the merger (small blue dots), and
have identified which features within the twin nuclei are associated with the
two super massive black holes known to inhabit the nuclear regions. The green
vertical line represents one second of arc, or 1,600 light years at the distance
of NGC 6240. Credit: C. Max, G. Canalizo, W. de Vries
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