Hidden Population of Powerful Black Holes Revealed in Large Sky Survey

Jan 09, 2008

A team of Sloan Digital Sky Survey (SDSS-II) scientists, led by Princeton University's Reinabelle Reyes and including astronomers at Penn State, has identified a large number of "hidden quasars" -- supermassive black holes in the centers of galaxies that are shrouded in light-absorbing dust and gas.

According to Donald Schneider, coauthor of the paper and Professor of Astronomy at Penn State, "If one examines a photograph of one of the hidden quasars we discovered, it appears to be just an ordinary galaxy, although quasars are typically are 10 to 100 times more luminous than the Milky Way Galaxy." Schneider is the chair of the SDSS-II science group that studies quasars, which are powered by glowing, super-heated gas as it swirls into black holes a billion times more massive than the Sun.

The research team, which will present its discovery on 9 January 2008 at the annual meeting of the American Astronomical Society in Austin, Texas, has submitted a paper describing the research for publication in the Astronomical Journal. Using the distinctive light-spectrum signature that even highly obscured quasars show as a marker, the SDSS-II team sifted through more than a million spectra to discover 887 hidden quasars, by far the largest sample of these objects ever found.

"A large survey like SDSS-II is important because quasars are about 10,000 times rarer than are normal galaxies," explains Reyes. "We determined how common hidden quasars are, especially the most luminous ones. Perhaps more interestingly, we determined how common they are relative to normal quasars," said team member Nadia Zakamska, a NASA Spitzer Fellow at the Institute for Advanced Study in Princeton. "We found that hidden quasars make up at least half of the quasars in the relatively recent Universe, implying that most of the powerful black holes in our neighborhood had previously been unrecognized."

Michael Strauss of Princeton University explains that powerful black holes are more common in the last eight billion years of cosmic history than had previously been thought. "Moreover, because the light from these hidden quasars previously had been unaccounted for, black holes turn out to be more efficient in converting the energy of in-falling matter into light than we had thought."

This result also has implications for theoretical models of quasars. "The relative numbers of hidden versus normal quasars tell us something about how dust and gas typically are distributed around these objects," explains Julian Krolik, a collaborator from Johns Hopkins University. "If the dust covers a large fraction of the area around a black hole, this object would more likely appear as a hidden quasar. So the large number of hidden quasars discovered by the SDSS team implies that most of the light emitted by quasars is actually obscured."

Source: Penn State University

Explore further: Image: NGC 6872 in the constellation of Pavo

add to favorites email to friend print save as pdf

Related Stories

Quasar may be embedded in unusually dusty galaxy

Oct 23, 2012

Hubble astronomers have looked at one of the most distant and brightest quasars in the universe and are surprised by what they did not see: the underlying host galaxy of stars feeding the quasar. The best ...

Giant black holes lurking in survey data

Oct 08, 2012

(Phys.org)—Scientists at the University of Cambridge have used cutting-edge infrared surveys of the sky to discover a new population of enormous, rapidly growing supermassive black holes in the early Universe. ...

Space telescope opens its X-ray eyes

Jun 29, 2012

NASA's Nuclear Spectroscopic Telescope Array, or NuSTAR, has snapped its first test images of the sizzling high-energy X-ray universe. The observatory, launched June 13, is the first space telescope with the ...

Astronomers discover biggest black holes ever (Update)

Dec 05, 2011

University of California, Berkeley, astronomers have discovered the largest black holes to date two monsters with masses equivalent to 10 billion suns that are threatening to consume anything, even light, ...

Recommended for you

Image: NGC 6872 in the constellation of Pavo

10 hours ago

This picture, taken by the NASA/ESA Hubble Space Telescope's Wide Field Planetary Camera 2 (WFPC2), shows a galaxy known as NGC 6872 in the constellation of Pavo (The Peacock). Its unusual shape is caused ...

Measuring the proper motion of a galaxy

10 hours ago

The motion of a star relative to us can be determined by measuring two quantities, radial motion and proper motion. Radial motion is the motion of a star along our line of sight. That is, motion directly ...

Gravitational waves according to Planck

Sep 22, 2014

Scientists of the Planck collaboration, and in particular the Trieste team, have conducted a series of in-depth checks on the discovery recently publicized by the Antarctic Observatory, which announced last ...

Infant solar system shows signs of windy weather

Sep 22, 2014

Astronomers using the Atacama Large Millimeter/submillimeter Array (ALMA) have observed what may be the first-ever signs of windy weather around a T Tauri star, an infant analog of our own Sun. This may help ...

Finding hints of gravitational waves in the stars

Sep 22, 2014

Scientists have shown how gravitational waves—invisible ripples in the fabric of space and time that propagate through the universe—might be "seen" by looking at the stars. The new model proposes that ...

How gamma ray telescopes work

Sep 22, 2014

Yesterday I talked about the detection of gamma ray bursts, intense blasts of gamma rays that occasionally appear in distant galaxies. Gamma ray bursts were only detected when gamma ray satellites were put ...

User comments : 0