Discovery of Growth-Spurt Era for Black Holes and Galaxies

Credit: NASA/CXC/Penn State/D. Alexander et al.

The illustration shows two young galaxies in the process of merging. The merger has triggered a prodigious burst of star formation and is providing fuel for the growth of the galaxies' central supermassive black holes.

The inset shows an image from the Chandra Deep Field-North of two central black holes in merging galaxies. Although the black holes appear to be very close in this image, they are actually about 70,000 light years apart. The different colors in the image are due to differences in X-ray absorption by gas and dust around the black holes with blue indicating more absorption than red.

By combining data from the Chandra Deep Field-North with observations at submillimeter and optical wavelengths, an international team of scientists has found evidence that many extremely luminous adolescent galaxies and their central black holes underwent a phenomenal spurt of growth 10 billion to 12 billion years ago. This growth spurt may have set the stage for the appearance of quasars, distant galaxies that contain the largest and most active black holes in the Universe.

The galaxies in the image are known as submillimeter galaxies, because they were originally identified by the James Clerk Maxwell submillimeter telescope (JCMT) on Mauna Kea in Hawaii. Hubble Space Telescope observations indicate that most of the submillimeter galaxies are actually two galaxies that are colliding and merging.

Recent sophisticated computer simulations have shown that such mergers drive gas toward the central regions of galaxies, triggering a burst of star formation and providing fuel for the growth of a central supermassive black hole. This explains the observational evidence that in submillimeter galaxies stars are forming at a prodigious rate at the same time that the central black holes are growing rapidly.

A combination of observation and theory suggests that in a few hundred million years the submillimeter galaxies will become quasars, and ultimately, large spherical galaxies that harbor central supermassive black holes with masses of about a billion Suns.

DISTANCE: About 11 billion light years (redshift z = 2.58)

NAME OF DOUBLE SOURCE: SMG 123616.1+621513

REFERENCES: D. Alexander et al. Nature 2005 April 7 issue (See also, astro-ph/0503453)

T. Di Matteo, et al. 2005, Nature 433, 604 (See also astro ph/0502199)

Additional information and images are available at:

http://chandra.harvard.edu

and

http://chandra.nasa.gov

Astronomers from Penn State are on the international research team that will announce its discovery of rapidly growing black holes in distant, massive, star-forming galaxies. The research will be published in the 7 April 2005 issue of the journal Nature. The Penn State scientists include Niel Brandt, professor of astronomy and astrophysics, and two former postdoctoral fellows in his lab: David Alexander, who now is a Royal Society Research Fellow at the University of Cambridge in the United Kingdom, and Franz Bauer, who now is a Chandra Fellow at Columbia University.

The research team used three observatories to view the universe in three different wavelengths: the Chandra X-ray Observatory in Earth orbit for X-rays, the Keck telescope in Hawaii for optical wavelengths, and the James Clerk Maxwell Telescope in Hawaii for submillimeter wavelengths. A major contribution of Brandt's lab is its work with the Chandra X-ray Observatory on the deep sky survey known as the Chandra Deep Field North. "This research has been a major effort in our lab for the past five years, and it will continue to deliver exciting scientific results for the next decade," Brandt says.

More information about the discovery is contained in the following NASA press release.

CONTACTS AT PENN STATE:

Niel Brandt: 814-865-3509, niel@astro.psu.edu

Barbara Kennedy (PIO): science@psu.edu, (+1) 814-863-4682

NASA's PRESS RELEASE

EMBARGOED until 1:00 p.m., Eastern U.S. time, on 6 April 2005

Era of Galaxy and Black Hole Growth Spurt Discovered

Dolores Beasley, NASA Headquarters, Washington, Dc. (Phone: 202/358-1753)

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

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

Distant galaxies undergoing intense bursts of star formation have been shown by NASA's Chandra X-ray Observatory to be fertile growing grounds for the largest black holes in the Universe. Collisions between galaxies in the early Universe may be the ultimate cause for both the accelerated star formation and black hole growth.

By combining the deepest X-ray image ever obtained with submillimeter and optical observations, an international team of scientists has found evidence that some extremely luminous adolescent galaxies and their central black holes underwent a phenomenal spurt of growth more than 10 billion years ago. This concurrent black hole and galaxy growth spurt is only seen in these galaxies and may have set the stage for the birth of quasars -- distant galaxies that contain the largest and most active black holes in the Universe.

"The extreme distances of these galaxies allow us to look back in time, and take a snapshot of how today's largest galaxies looked when they were producing most of their stars and growing black holes, " said David Alexander of the University of Cambridge, UK, and lead author of a paper in the April 7, 2005 issue of Nature that describes this work.

The galaxies studied by Alexander and his colleagues are known as submillimeter galaxies, so-called because they were originally identified by the James Clerk Maxwell submillimeter telescope (JCMT) on Mauna Kea in Hawaii. The submillimeter observations along with optical data from Keck indicate these galaxies had an unusually large amount of gas. The gas in each galaxy was forming into stars at a rate of about one per day, or 100 times the present rate in the Milky Way galaxy. The Chandra X-ray data show that the supermassive black holes in the galaxies were also growing at the same time.

These galaxies are very faint and it is only with the deepest observations of the Universe that they can be detected at all. "The deeper we look into the Universe with Chandra, the more fascinating things we find" says Niel Brandt of Penn State University in University Park. "Who knows what nature has in store for us as we push the boundaries yet further."

The X-ray observations also showed that the black holes are surrounded by a dense shroud of gas and dust. This is probably the material that will be consumed by the growing black holes.

Hubble Space Telescope observations indicate that most of the submillimeter galaxies are actually two galaxies that are colliding and merging. Recent sophisticated computer simulations performed by Tiziana Di Matteo of Carnegie Mellon University in Pittsburgh, Penn., and her collaborators have shown that such mergers drive gas toward the central regions of galaxies, triggering a burst of star formation and providing fuel for the growth of a central black hole.

"It is exciting that these recent observations are in good agreement with our simulation," says Di Matteo, "We seem to be converging on a consistent picture of galaxy formation with both observations and theory." In particular, this work will help scientists to understand the observed link in the present epoch between the total mass of stars in the central bulges of large galaxies and the size of their central, supermassive black holes.

The James Clerk Maxwell Telescope (JCMT) is operated on behalf of the United Kingdom, Canada & Netherlands by the Joint Astronomy Centre. With its 15-meter (50-foot) diameter dish the JCMT detects light with "submillimeter" wavelengths, between infrared light and radio waves on the wavelength scale. The W. M. Keck Observatory is operated by the California Association for Research in Astronomy.

NASA's Marshall Space Flight Center, Huntsville, Ala., manages the Chandra program for NASA's Science Mission Directorate, Washington. Northrop Grumman of Redondo Beach, Calif., was the prime development contractor for the observatory. The Smithsonian Astrophysical Observatory controls science and flight operations from the Chandra X-ray Center in Cambridge, Mass.

Additional information and images are available at:

http://chandra.harvard.edu

and

http://chandra.nasa.gov