Andrew Yee
January 13th 06, 05:23 AM
Public Affairs Office
Harvard-Smithsonian Center for Astrophysics
Cambridge, Massachusetts
For more information, contact:
David A. Aguilar, Director of Public Affairs
Harvard-Smithsonian Center for Astrophysics
617-495-7462
Christine Pulliam, Public Affairs Specialist
Harvard-Smithsonian Center for Astrophysics
Phone: 617-495-7463, Fax: 617-495-7016
Release No.: 06-08
For Release: EMBARGOED until 10:00 a.m. EST, Thursday, January 12, 2006
Growing Supermassive Black Holes from Seeds
Washington, DC -- Astronomers announced today that they have found the
first sample of intermediate-mass black holes in active galaxies -- a
discovery that will help in understanding the early universe. "These are
local analogues of the 'seed' black holes from which supermassive black
holes formed," said Ms. Jenny E. Greene of the Harvard-Smithsonian Center
for Astrophysics (CfA). Greene presented these results with Dr. Luis C. Ho
of Carnegie Observatories at the 207th meeting of the American
Astronomical Society in Washington, D.C.
"Supermassive black holes (with masses of millions to billions of times
the mass of the Sun) are found in the centers of most, if not all, massive
galaxies, and the black hole masses scale with the galaxy masses, so that
larger black holes reside in larger galaxies," said Greene. "We want to
understand how this connection is established, and more specifically, what
role black holes play in the evolution of galaxies."
Black holes probably evolve as material, such as gas, dust, stars and even
other black holes, gets sucked in by the strong gravitational pull.
"However, we cannot observe the starting conditions of the black holes
directly," said Ho. "How massive were they? How and when were they made?
These are crucial questions to answer if we want to understand how black
holes impact the growth of galaxies."
The black hole "seeds" originally may have formed from the explosions of
the first stars or from the collapse of clumps of gas in the early
universe. Each of these different formation scenarios leads to very
different numbers of intermediate-mass black holes left over in the
universe today. Until now, few good candidates had been found.
Greene sifted for intermediate-mass black holes in the first data release
from the Sloan Digital Sky Survey, a multi-year comprehensive survey of
one quarter of the sky. (The first public data release from the SDSS
contains information on 50 million objects, including spectra and
redshifts for almost 200,000 objects.)
In her thesis work, Greene identified objects with black holes by
detecting the light from gas moving at extremely high velocities close to
the black hole. Using the speed of the gas, and an estimate of the
distance of the gas from the black hole, it was possible to estimate a
black hole mass for each galaxy. She then selected all of the objects with
masses less than one million solar masses, yielding a total of 19 new
black holes.
"This sample provides the only currently available observational
constraints on the properties of seed black holes in the early universe,"
said Greene.
Besides the formation of supermassive black holes seen today, this data
set may help with another question -- the re-ionization of the universe.
Present theory holds that soon after the Big Bang, the universe was filled
mostly with hydrogen and helium that was ionized -- too hot to remain in a
stable state. Over about 300,000 years, the universe expanded and cooled,
and the gases began to recombine and stabilize to neutral states. This
neutral gas acted as an opaque fog blocking the transmission of light. The
universe then entered the dark ages, estimated to have lasted about half a
billion years.
At the same time, matter was clumping together to form the first stars,
galaxies and quasars. (Quasars are incredibly bright objects powered by
supermassive black holes.) The radiation from these new objects made the
opaque gas of the universe become transparent by splitting atoms of
hydrogen into free electrons and protons, thus re-ionizing the universe.
"These seed black holes presumably occasionally lit up as 'mini-quasars.'
It is still an open question whether the emission from small black holes
played an important role in re-ionizing the universe, ending the cosmic
dark ages," said Greene. "Our measurements of the light radiated by
low-mass black holes will help us decide whether or not black holes in
this mass range could have contributed significantly to re-ionization."
Gravity waves also could point to an early population of
intermediate-sized black holes. When two black holes merge, their
coalescence sends out gravity waves, or ripples in space-time.
"Gravitational wave experiments, especially the Laser Interferometric
Space Antenna (LISA) expect to be very sensitive to the merging of
100,000-solar-mass black holes," said Greene. "The objects we identified
will give clues to help the LISA team determine how many black hole
collisions they may expect to find."
Headquartered in Cambridge, Mass., the Harvard-Smithsonian Center for
Astrophysics (CfA) is a joint collaboration between the Smithsonian
Astrophysical Observatory and the Harvard College Observatory. CfA
scientists, organized into six research divisions, study the origin,
evolution and ultimate fate of the universe.
Note to editors: A high-resolution images to accompany this release is
online at
http://www.cfa.harvard.edu/press/pr0608image.html
Harvard-Smithsonian Center for Astrophysics
Cambridge, Massachusetts
For more information, contact:
David A. Aguilar, Director of Public Affairs
Harvard-Smithsonian Center for Astrophysics
617-495-7462
Christine Pulliam, Public Affairs Specialist
Harvard-Smithsonian Center for Astrophysics
Phone: 617-495-7463, Fax: 617-495-7016
Release No.: 06-08
For Release: EMBARGOED until 10:00 a.m. EST, Thursday, January 12, 2006
Growing Supermassive Black Holes from Seeds
Washington, DC -- Astronomers announced today that they have found the
first sample of intermediate-mass black holes in active galaxies -- a
discovery that will help in understanding the early universe. "These are
local analogues of the 'seed' black holes from which supermassive black
holes formed," said Ms. Jenny E. Greene of the Harvard-Smithsonian Center
for Astrophysics (CfA). Greene presented these results with Dr. Luis C. Ho
of Carnegie Observatories at the 207th meeting of the American
Astronomical Society in Washington, D.C.
"Supermassive black holes (with masses of millions to billions of times
the mass of the Sun) are found in the centers of most, if not all, massive
galaxies, and the black hole masses scale with the galaxy masses, so that
larger black holes reside in larger galaxies," said Greene. "We want to
understand how this connection is established, and more specifically, what
role black holes play in the evolution of galaxies."
Black holes probably evolve as material, such as gas, dust, stars and even
other black holes, gets sucked in by the strong gravitational pull.
"However, we cannot observe the starting conditions of the black holes
directly," said Ho. "How massive were they? How and when were they made?
These are crucial questions to answer if we want to understand how black
holes impact the growth of galaxies."
The black hole "seeds" originally may have formed from the explosions of
the first stars or from the collapse of clumps of gas in the early
universe. Each of these different formation scenarios leads to very
different numbers of intermediate-mass black holes left over in the
universe today. Until now, few good candidates had been found.
Greene sifted for intermediate-mass black holes in the first data release
from the Sloan Digital Sky Survey, a multi-year comprehensive survey of
one quarter of the sky. (The first public data release from the SDSS
contains information on 50 million objects, including spectra and
redshifts for almost 200,000 objects.)
In her thesis work, Greene identified objects with black holes by
detecting the light from gas moving at extremely high velocities close to
the black hole. Using the speed of the gas, and an estimate of the
distance of the gas from the black hole, it was possible to estimate a
black hole mass for each galaxy. She then selected all of the objects with
masses less than one million solar masses, yielding a total of 19 new
black holes.
"This sample provides the only currently available observational
constraints on the properties of seed black holes in the early universe,"
said Greene.
Besides the formation of supermassive black holes seen today, this data
set may help with another question -- the re-ionization of the universe.
Present theory holds that soon after the Big Bang, the universe was filled
mostly with hydrogen and helium that was ionized -- too hot to remain in a
stable state. Over about 300,000 years, the universe expanded and cooled,
and the gases began to recombine and stabilize to neutral states. This
neutral gas acted as an opaque fog blocking the transmission of light. The
universe then entered the dark ages, estimated to have lasted about half a
billion years.
At the same time, matter was clumping together to form the first stars,
galaxies and quasars. (Quasars are incredibly bright objects powered by
supermassive black holes.) The radiation from these new objects made the
opaque gas of the universe become transparent by splitting atoms of
hydrogen into free electrons and protons, thus re-ionizing the universe.
"These seed black holes presumably occasionally lit up as 'mini-quasars.'
It is still an open question whether the emission from small black holes
played an important role in re-ionizing the universe, ending the cosmic
dark ages," said Greene. "Our measurements of the light radiated by
low-mass black holes will help us decide whether or not black holes in
this mass range could have contributed significantly to re-ionization."
Gravity waves also could point to an early population of
intermediate-sized black holes. When two black holes merge, their
coalescence sends out gravity waves, or ripples in space-time.
"Gravitational wave experiments, especially the Laser Interferometric
Space Antenna (LISA) expect to be very sensitive to the merging of
100,000-solar-mass black holes," said Greene. "The objects we identified
will give clues to help the LISA team determine how many black hole
collisions they may expect to find."
Headquartered in Cambridge, Mass., the Harvard-Smithsonian Center for
Astrophysics (CfA) is a joint collaboration between the Smithsonian
Astrophysical Observatory and the Harvard College Observatory. CfA
scientists, organized into six research divisions, study the origin,
evolution and ultimate fate of the universe.
Note to editors: A high-resolution images to accompany this release is
online at
http://www.cfa.harvard.edu/press/pr0608image.html