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Discovery of Earliest Known Black Holes

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17 March 2010
Click on image for high-resolution file.
Brandt_cloud_3-2010
Brandt_cloud_3-2010
What did the first supermassive black holes -- the first quasars -- look like? The very early universe didn't have any dust, so the most primitive quasars also should be dust-free. But nobody had seen such pristine quasars until recently, when the Spitzer telescope spied two of them about 13 billion light-years away. The findings, published in the 18 March 2010 issue of the journal Nature, will help astronomers understand the roots of our universe, and how the very first black holes, galaxies, and stars all came to be. This artist's impression was drawn before the discovery by Spitzer. It depicts how a primordial quasar might have looked during a slightly later stage in the evolution of the universe, when some clouds of gas and some stars had begun to accumulate in the early universe.
Image credit: European Space Agency and Wolfram Freudling (Space Telescope-European Coordinating Facility/European Southern Observatory, Germany)

Astronomers have discovered what appear to be two of the earliest and most primitive supermassive black holes known. The discovery, based on observations with the NASA's Spitzer Space Telescope and other space observatories, will be published in the 18 March 2010 edition of the scientific journal Nature.

Black holes are beastly distortions of space and time. The most massive and active ones lurk at the cores of galaxies, and are usually surrounded by doughnut-shaped structures of dust and gas that feed and sustain the growing black holes. These hungry supermassive black holes are called quasars.

The very early universe didn't have any dust, so the most primitive quasars also should be dust-free. But nobody had seen such pristine quasars -- until now, when the Spitzer telescope spied two of them about 13 billion light-years away. The findings will help astronomers understand the roots of our universe, and how the very first black holes, galaxies, and stars all came to be.

"The main goal of this collaboration is to determine if these very first quasars -- which are very distant from Earth in space and time -- are feeding and growing in the same way as do quasars that are closer to Earth," said Niel Brandt, professor of astronomy and astrophysics at Penn State University. "We have found what are likely first-generation quasars, born in a dust-free medium and at the earliest stages of evolution," said Linhua Jiang of University of Arizona, Tucson. Jiang is the first author of the research paper.

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This artist's impression shows a quasar during later stages of the evolution of the universe, with its supermassive black hole surrounded by a torus of thick dust and gas.
Image credit: NASA/CXC/M.Weiss

This paper is one result of a decade-long collaboration to measure a wide range of energies emitted by the first quasars to form in the universe -- energies low as infrared to as high as X-rays. Brandt's research group has led much of the X-ray work in this collaboration, and has discovered that the X-ray emission from the first quasars is remarkably similar to that of local quasars.

X-rays, ultraviolet light, and optical light stream out from quasars as these supermassive black holes consume the gas surrounding them, a process called accretion. "For about a decade, our X-ray and optical measurements have provided increasingly strong evidence that the inner accretion flows of the first quasars are remarkably similar to those of garden-variety quasars in the local universe. It thus is unexpected and exciting to find a small number of quasars that, in their infrared properties, clearly differ from local objects," Brandt said.

"Quasars emit enormous amount of light, making them detectable literally at the edge of observable universe," said Xiaohui Fan, a coauthor of the paper at the University of Arizona. The two quasars, called J0005-0006 and J0303-0019, were first discovered by Fan, Jiang, and their colleagues in 2004 and 2007 using visible-light data from the Sloan Digital Sky Survey. NASA's Chandra X-ray Observatory also had observed X-rays from one of the objects in 2005. Fan's research group led the infrared work in this collaboration.

When the astronomy team set out to observe J0005-0006 and J0303-0019 with Spitzer between 2006 and 2009, the objects didn't stand out much from the usual quasar bunch. Spitzer measured infrared light from the two objects along with eighteen others, all belonging to a class of the most distant quasars known. Each quasar is anchored by a supermassive black hole weighing more than 100 million suns.

The Spitzer data showed that, of the 20 quasars, J0005-0006 and J0303-0019 lacked the characteristic signatures of hot dust. Spitzer's infrared sight makes it ideally suited to detect the warm glow of dust that has been heated by the feeding black holes.

Click on image for high-resolution file.

Brandt_A_Young_Black_Hole_3-2010
Brandt_A_Young_Black_Hole_3-2010

Prehistoric Black Hole
This artist's conception illustrates one of the most primitive supermassive black holes known (central black dot) at the core of a young, star-rich galaxy. Astronomers using NASA's Spitzer Space Telescope have uncovered two of these early objects, dating back to about 13 billion years ago.

The monstrous black holes are among the most distant known, and appear to be in the very earliest stages of formation, earlier than any observed so far. Unlike all other supermassive black holes probed to date, this primitive duo, called J0005-0006 and J0303-0019, lacks dust.

As the drawing shows, gas swirls around a black hole in what is called an accretion disk. Usually, the accretion disk is surrounded by a doughnut-like dusty structure called a dust torus. But for the primitive black holes, the dust tori are missing and only gas disks are observed. This is because the early universe was clean as a whistle. Enough time had not passed for molecules to clump together into dust particles. Some black holes forming in this era thus started out lacking dust. As they grew, gobbling up more and more mass, they are thought to have accumulated dusty rings.

This illustration also shows how supermassive black holes can distort space and light around them (see warped stars behind black hole). Stars from the galaxy can be seen sprinkled throughout, and distant mergers between other galaxies are illustrated in the background.

Image credit: NASA/JPL-Caltech

"We think these early black holes are forming around the time when dust was first forming in the universe, less than one billion years after the Big Bang," said Fan. "The primordial universe did not contain any molecules that could coagulate to form dust. The elements necessary for this process were produced and pumped into the universe later by stars."

The astronomers also observed that the amount of hot dust in a quasar increased with the mass of its black hole. As a black hole grows, dust has more time to build up around it. J0005-0006 and J0303-0019 have the smallest black holes known in the early universe, indicating they are particularly young, and at a stage when dust has not yet formed around them.

[ Whitney Clavin / Barbara Kennedy ]

CONTACTS
Niel Brandt: (+1)814-865-3509, niel@astro.psu.edu
Barbara Kennedy (PIO at Penn State): (+1)814-863-4682, science@psu.edu

MORE INFORMATION
In addition to Brandt, Jiang, and Fan, other authors of the paper include Chris L. Carilli of the National Radio Astronomy Observatory, Socorro, N.M.; Eiichi Egami of the University of Arizona; Dean C. Hines of the Space Science Institute, Boulder, Colo.; Jaron D. Kurk of the Max Planck Institute for Extraterrestrial Physics, Germany; Gordon T. Richards of Drexel University, Philadephia, Pa.; Yue Shen of the Harvard Smithsonian Center for Astrophysics, Cambridge, Mass.; Michael A. Strauss of Princeton, N.J.; Marianne Vestergaard of the University of Arizona and Niels Bohr Institute in Denmark; and Fabian Walter of Max Planck Institute for Astronomy, Germany. Fan was based in part at Max Planck Institute for Astronomy when this research was conducted.

NASA's Jet Propulsion Laboratory in Pasadena, California, manages the Spitzer Space Telescope mission for NASA's Science Mission Directorate in Washington, D.C. Science operations are conducted at the Spitzer Science Center at the California Institute of Technology in Pasadena. Caltech manages JPL for NASA. The Spitzer observations were made before the telescope ran out of its liquid coolant in May 2009, beginning its "warm" mission. For more information about Spitzer, visit http://www.spitzer.caltech.edu/spitzer and http://www.nasa.gov/spitzer.

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