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: Hubble, the telescope that revolutionized our view of space

Related Stories

Data deluge: MLB rolls out Statcast analytics on Tuesday

8 minutes ago

Which outfielder sprints the fastest and runs the longest to snag line drives into the gap? Which shortstop is best at throwing from the grass to nip the runner at first? Which catcher gets the ball to second ...

Air pollution levels drop in China: Greenpeace

34 minutes ago

Air pollution levels in some of China's smoggiest cities fell by nearly a third in the first quarter of this year, environmental campaign group Greenpeace said on Tuesday.

Obama in fresh push on climate change

53 minutes ago

US President Barack Obama will travel to Florida's Everglades Wednesday hoping to reframe the debate on climate change ahead of a vital few months that will shape his environmental legacy.

Recommended for you

Radio astronomy backed by big data projects

19 minutes ago

As the leading edge of the Square Kilometre Array (SKA) project, the Murchison Widefield Array (MWA) radio telescope is at the forefront of the big data challenges facing radio astronomy, presenting and solving ...

Black hole hunters tackle a cosmic conundrum

17 hours ago

Dartmouth astrophysicists and their colleagues have not only proven that a supermassive black hole exists in a place where it isn't supposed to be, but in doing so have opened a new door to what things were ...

Image: Thor's Helmet nebula in the X-ray spectrum

Apr 20, 2015

This brightly coloured scene shows a giant cloud of glowing gas and dust known as NGC 2359. This is also dubbed the Thor's Helmet nebula, due to the arching arms of gas stemming from the central bulge and ...

User comments : 0

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.