Unmasking galaxies’ hidden black holes
Hubble Space telescope image of the spiral galaxy NGC4526,
overlaid with molecular gas observations (purple) from CARMA. The black hole sits in the very center of the galaxy.
Picture credit: NASA/ESA and Timothy A. Davis.
January 31, 2013
By Robert Sanders
Berkeley — Most astronomers suspect that a massive black hole lurks at the center of most if not all galaxies,
but only a few dozen examples are known out of billions of galaxies in the cosmos.
Now astronomers have developed a quick technique that could potentially uncover and weigh ten times more massive black holes
than are now known. Using the Combined Array for Research in Millimeter-wave Astronomy (CARMA) in California’s Owens Valley,
UC Berkeley and European astronomers tracked carbon monoxide gas swirling around the center of a galaxy 53 million light years
from Earth. Based on the gas’s motion, they concluded that the galaxy, NGC4526, harbored a massive black hole about 450 million
times the mass of the sun – 100 times larger than the black hole at the center of our Milky Way Galaxy.
“Because almost all spiral galaxies like the Milky Way and about one-quarter of large galaxies of the type we observed have
molecular gas, this interferometry technique applies broadly, and raises the real probability of getting a large sample of
black holes from all sorts of galaxies at much greater distances,” said Leo Blitz, UC Berkeley professor of astronomy and
coauthor of a paper describing the procedure that appeared in the Jan. 31 issue of Nature.
The Atacama Large Millimeter/submillimeter Array (ALMA) now nearing completion in Chile could potentially measure black hole masses
at the centers of hundreds of galaxies in as little as 10 minutes each, “shedding light on the mysterious co-evolution of
black holes and galaxies,” added team leader Timothy A. Davis of the European Southern Observatory, which is based in Germany.
• A black-hole mass measurement from molecular gas kinematics in NGC4526 (Nature paper)
Timothy Davis’s Web site summarizing the results
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