Supermassive Black Holes May Frequently Roam
Thu May 27, 2010 2:27 am » by Kingz
Supermassive Black Holes May Frequently Roam
ScienceDaily (May 26, 2010)
A team of astronomy researchers at Florida Institute of Technology and Rochester Institute of Technology in the United States and University of Sussex in the United Kingdom, find that the supermassive black hole (SMBH) at the center of the most massive local galaxy (M87) is not where it was expected. Their research, conducted using the Hubble Space Telescope (HST), concludes that the SMBH in M87 is displaced from the galaxy center.
Hubble Space Telescope Images of M87. At right, a large scale image taken with the Wide-Field/Planetary Camera-2 from 1998 (NASA and the Hubble Heritage Team (STScI/AURA), J. A. Biretta, W. B. Sparks, F. D. Macchetto, E. S. Perlman). The two images at left show an image taken in 2006 with the Advanced Camera for Surveys' High Resolution Channel. The position of the supermassive black hole is indicated by the black dot in the lower left panel, and a knot in the jet (HST-1), which was flaring in 2006, is also indicated on this panel. The red dot indicates the center of the galaxy's light distribution, which is offset from the position of the black hole by 22 +/- 3 light years. (Credit: (NASA and the Hubble Heritage Team (STScI/AURA), J. A. Biretta, W. B. Sparks, F. D. Macchetto, E. S. Perlman).)
The most likely cause for this SMBH to be off center is a previous merger between two older, less massive, SMBHs. "We also find, however, that the iconic M87 jet may have pushed the SMBH away from the galaxy center," said Daniel Batcheldor, Florida Tech assistant professor in the Department of Physics and Space Sciences, who led the investigation.
The study of M87 is part of a wider HST project directed by Andrew Robinson, professor of physics at RIT. "What may well be the most interesting thing about this work is the possibility that what we found is a signpost of a black hole merger, which is of interest to people looking for gravitational waves and for people modeling these systems as a demonstration that black holes really do merge," says Robinson. "The theoretical prediction is that when two black holes merge, the newly combined black hole receives a 'kick' due to the emission of gravitational waves, which can displace it from the center of the galaxy."
David Merritt, professor of physics at RIT, adds: "Once kicked, a supermassive black hole can take millions or billions of years to return to rest, especially at the center of a large, diffuse galaxy like M87. So searching for displacements is an effective way to constrain the merger history of galaxies."
Jets, such as the one in M87, are commonly found in a class of objects called Active Galactic Nuclei. It is commonly believed that supermassive black holes can become active as a result of the merger between two galaxies, the infall of material into the center of the galaxy, and the subsequent merger between their black holes.
Therefore, it is very possible that this finding could also be linked to how active galaxies -- including quasars, the most luminous objects in the universe -- are born and how their jets are formed.
This research will be presented at the American Astronomical Society (AAS) Conference on May 25 in Miami, Fla. It will also be published in The Astrophysical Journal Letters peer-reviewed scientific journal.
Because many galaxies have similar properties to M87, it is likely that SMBHs are commonly offset from their host galaxy centers. The potential offsets, however, would be very subtle and researchers would rely on the Hubble Space Telescope to detect them.
"Unfortunately, the highest spatial resolution camera onboard HST could not be revived during the recent servicing mission. This means we have to rely on the huge archive of HST data to find more of these vagrant SMBHs, as we did for M87," added Batcheldor.
Regardless of the displacement mechanism, the implication of this result is a necessary shift in the classic SMBH paradigm; no longer can it be assumed that all SMBHs reside at the centers of their host galaxies. This may result in some interesting impacts on a number of fundamental astronomical areas, and some interesting questions.
For example, how would an accreting (growing by the gravitational attraction of matter) or quiescent SMBH interact with the surrounding nuclear environment as it moves through the bulge? What are the effects on the standard orientation-based unified model of active galactic nuclei and how have dynamical models of the SMBH mass been centered if the SMBH is quiescent?
Especially thought-provoking, added Eric Perlman, associate professor of physics and space sciences at Florida Tech, is that our own galaxy is expected to merge with the Andromeda galaxy in about three billion years. "The result of that merger will likely be an active elliptical galaxy, similar to M87. Both our galaxy and Andromeda have SMBHs in their centers, so our result suggests that after the merger, the SMBH may wander in the galaxy's nucleus for billions of years."
David Axon, Dean of Mathematical and Physical Sciences at Sussex, concludes by saying that "In current galaxy formation scenarios galaxies are thought to be assembled by a process of merging. We should therefore expect that binary black holes and post coalescence recoiling black holes, like that in M87, are very common in the cosmos."
Story Source:
Adapted from materials provided by Florida Institute of Technology.
http://www.fit.edu/
Journal Reference:
1. D. Batcheldor, A. Robinson, D. J. Axon, E. S. Perlman, D. Merritt. A Displaced Supermassive Black Hole in M87. The Astrophysical Journal Letters, 12 May 2010
http://arxiv.org/abs/1005.2173
http://www.sciencedaily.com/releases/20 ... 154004.htm
ScienceDaily (May 26, 2010)
A team of astronomy researchers at Florida Institute of Technology and Rochester Institute of Technology in the United States and University of Sussex in the United Kingdom, find that the supermassive black hole (SMBH) at the center of the most massive local galaxy (M87) is not where it was expected. Their research, conducted using the Hubble Space Telescope (HST), concludes that the SMBH in M87 is displaced from the galaxy center.
Hubble Space Telescope Images of M87. At right, a large scale image taken with the Wide-Field/Planetary Camera-2 from 1998 (NASA and the Hubble Heritage Team (STScI/AURA), J. A. Biretta, W. B. Sparks, F. D. Macchetto, E. S. Perlman). The two images at left show an image taken in 2006 with the Advanced Camera for Surveys' High Resolution Channel. The position of the supermassive black hole is indicated by the black dot in the lower left panel, and a knot in the jet (HST-1), which was flaring in 2006, is also indicated on this panel. The red dot indicates the center of the galaxy's light distribution, which is offset from the position of the black hole by 22 +/- 3 light years. (Credit: (NASA and the Hubble Heritage Team (STScI/AURA), J. A. Biretta, W. B. Sparks, F. D. Macchetto, E. S. Perlman).)
The most likely cause for this SMBH to be off center is a previous merger between two older, less massive, SMBHs. "We also find, however, that the iconic M87 jet may have pushed the SMBH away from the galaxy center," said Daniel Batcheldor, Florida Tech assistant professor in the Department of Physics and Space Sciences, who led the investigation.
The study of M87 is part of a wider HST project directed by Andrew Robinson, professor of physics at RIT. "What may well be the most interesting thing about this work is the possibility that what we found is a signpost of a black hole merger, which is of interest to people looking for gravitational waves and for people modeling these systems as a demonstration that black holes really do merge," says Robinson. "The theoretical prediction is that when two black holes merge, the newly combined black hole receives a 'kick' due to the emission of gravitational waves, which can displace it from the center of the galaxy."
David Merritt, professor of physics at RIT, adds: "Once kicked, a supermassive black hole can take millions or billions of years to return to rest, especially at the center of a large, diffuse galaxy like M87. So searching for displacements is an effective way to constrain the merger history of galaxies."
Jets, such as the one in M87, are commonly found in a class of objects called Active Galactic Nuclei. It is commonly believed that supermassive black holes can become active as a result of the merger between two galaxies, the infall of material into the center of the galaxy, and the subsequent merger between their black holes.
Therefore, it is very possible that this finding could also be linked to how active galaxies -- including quasars, the most luminous objects in the universe -- are born and how their jets are formed.
This research will be presented at the American Astronomical Society (AAS) Conference on May 25 in Miami, Fla. It will also be published in The Astrophysical Journal Letters peer-reviewed scientific journal.
Because many galaxies have similar properties to M87, it is likely that SMBHs are commonly offset from their host galaxy centers. The potential offsets, however, would be very subtle and researchers would rely on the Hubble Space Telescope to detect them.
"Unfortunately, the highest spatial resolution camera onboard HST could not be revived during the recent servicing mission. This means we have to rely on the huge archive of HST data to find more of these vagrant SMBHs, as we did for M87," added Batcheldor.
Regardless of the displacement mechanism, the implication of this result is a necessary shift in the classic SMBH paradigm; no longer can it be assumed that all SMBHs reside at the centers of their host galaxies. This may result in some interesting impacts on a number of fundamental astronomical areas, and some interesting questions.
For example, how would an accreting (growing by the gravitational attraction of matter) or quiescent SMBH interact with the surrounding nuclear environment as it moves through the bulge? What are the effects on the standard orientation-based unified model of active galactic nuclei and how have dynamical models of the SMBH mass been centered if the SMBH is quiescent?
Especially thought-provoking, added Eric Perlman, associate professor of physics and space sciences at Florida Tech, is that our own galaxy is expected to merge with the Andromeda galaxy in about three billion years. "The result of that merger will likely be an active elliptical galaxy, similar to M87. Both our galaxy and Andromeda have SMBHs in their centers, so our result suggests that after the merger, the SMBH may wander in the galaxy's nucleus for billions of years."
David Axon, Dean of Mathematical and Physical Sciences at Sussex, concludes by saying that "In current galaxy formation scenarios galaxies are thought to be assembled by a process of merging. We should therefore expect that binary black holes and post coalescence recoiling black holes, like that in M87, are very common in the cosmos."
Story Source:
Adapted from materials provided by Florida Institute of Technology.
http://www.fit.edu/
Journal Reference:
1. D. Batcheldor, A. Robinson, D. J. Axon, E. S. Perlman, D. Merritt. A Displaced Supermassive Black Hole in M87. The Astrophysical Journal Letters, 12 May 2010
http://arxiv.org/abs/1005.2173
http://www.sciencedaily.com/releases/20 ... 154004.htm
The Map Is Not The Territory, The Word Is Not The Object....
_______________________________________________________________
_______________________________________________________________
Thu May 27, 2010 2:28 am » by Kingz
Nearby Black Hole Is Feeble and Unpredictable
ScienceDaily (May 25, 2010)
For over 10 years, NASA's Chandra X-ray Observatory has repeatedly observed the Andromeda Galaxy for a combined total of nearly one million seconds. This unique data set has given astronomers an unprecedented view of the nearest supermassive black hole outside our own Galaxy.
The large image here shows an optical view, with the Digitized Sky Survey, of the Andromeda Galaxy, otherwise known as M31. The inset shows Chandra images of a small region in the center of Andromeda. The image on the left shows a sum of Chandra images taken before January 2006 and the image on the right shows a sum of images taken after January 2006. Before 2006, three X-ray sources are clearly visible, including one faint source close to the center of the image. After 2006, a fourth source, called M31*, appears just below and to the right of the central source, produced by material falling onto the supermassive black hole in M31. (Credit: X-ray (NASA/CXC/SAO/Li et al.), Optical (DSS))
Astronomers think that most galaxies -- including the Milky Way -- contain giant black holes at their cores that are millions of times more massive than the Sun. At a distance of just under 3 million light years from Earth, Andromeda (also known as M31) is relatively close and provides an opportunity to study its black hole in great detail.
Just like the one in the center of the Milky Way, the black hole in Andromeda is surprisingly quiet. In fact, Andromeda's black hole, known as M31*, is ten to one hundred thousand times fainter in X-ray light that astronomers might expect given the reservoir of gas around it.
"The black holes in both Andromeda and the Milky Way are incredibly feeble," said Zhiyuan Li of the Harvard-Smithsonian Center for Astrophysics (CfA) in Cambridge, Mass. "These two 'anti-quasars' provide special laboratories for us to study some of the dimmest type of accretion even seen onto a supermassive black hole."
The decade-long study by Chandra reveals that M31* was in a very dim, or quiet, state before 2006. However, on January 6, 2006, the black hole became more than a hundred times brighter, suggesting an outburst of X-rays. This was the first time such an event had been seen from a supermassive black hole in the nearby, local universe.
After the outburst, M31* entered another relatively dim state, but was almost ten times brighter on average than before 2006. The outburst suggests a relatively high rate of matter falling onto M31* followed by a smaller, but still significant rate.
"We have some ideas about what's happening right around the black hole in Andromeda, but the truth is we still don't really know the details," said Christine Jones, also of the CfA.
The overall brightening since 2006 could be caused by M31* capturing winds from an orbiting star, or by a gas cloud that spiraled into the black hole. The increase in the rate of material falling towards the black hole is thought to drive an X-ray brightening of a relativistic jet.
The cause of the outburst in 2006 is even less clear, but it could be due to a sudden release of energy, such as magnetic fields in a disk around the black hole that suddenly connect and become more powerful.
"It's important to figure out what's going on here because the accretion of matter onto these black holes is one of the most fundamental processes governing the evolution of galaxies," said Li, who presented these results at the 216th meeting of the American Astronomical Society meeting in Miami, FL.
These results imply that the feeble, but erratic behavior of the black hole in the Milky Way may be typical for present-day supermassive black holes.
Story Source:
Adapted from materials provided by Harvard-Smithsonian Center for Astrophysics.
http://www.cfa.harvard.edu/
http://www.sciencedaily.com/releases/20 ... 094902.htm
ScienceDaily (May 25, 2010)
For over 10 years, NASA's Chandra X-ray Observatory has repeatedly observed the Andromeda Galaxy for a combined total of nearly one million seconds. This unique data set has given astronomers an unprecedented view of the nearest supermassive black hole outside our own Galaxy.
The large image here shows an optical view, with the Digitized Sky Survey, of the Andromeda Galaxy, otherwise known as M31. The inset shows Chandra images of a small region in the center of Andromeda. The image on the left shows a sum of Chandra images taken before January 2006 and the image on the right shows a sum of images taken after January 2006. Before 2006, three X-ray sources are clearly visible, including one faint source close to the center of the image. After 2006, a fourth source, called M31*, appears just below and to the right of the central source, produced by material falling onto the supermassive black hole in M31. (Credit: X-ray (NASA/CXC/SAO/Li et al.), Optical (DSS))
Astronomers think that most galaxies -- including the Milky Way -- contain giant black holes at their cores that are millions of times more massive than the Sun. At a distance of just under 3 million light years from Earth, Andromeda (also known as M31) is relatively close and provides an opportunity to study its black hole in great detail.
Just like the one in the center of the Milky Way, the black hole in Andromeda is surprisingly quiet. In fact, Andromeda's black hole, known as M31*, is ten to one hundred thousand times fainter in X-ray light that astronomers might expect given the reservoir of gas around it.
"The black holes in both Andromeda and the Milky Way are incredibly feeble," said Zhiyuan Li of the Harvard-Smithsonian Center for Astrophysics (CfA) in Cambridge, Mass. "These two 'anti-quasars' provide special laboratories for us to study some of the dimmest type of accretion even seen onto a supermassive black hole."
The decade-long study by Chandra reveals that M31* was in a very dim, or quiet, state before 2006. However, on January 6, 2006, the black hole became more than a hundred times brighter, suggesting an outburst of X-rays. This was the first time such an event had been seen from a supermassive black hole in the nearby, local universe.
After the outburst, M31* entered another relatively dim state, but was almost ten times brighter on average than before 2006. The outburst suggests a relatively high rate of matter falling onto M31* followed by a smaller, but still significant rate.
"We have some ideas about what's happening right around the black hole in Andromeda, but the truth is we still don't really know the details," said Christine Jones, also of the CfA.
The overall brightening since 2006 could be caused by M31* capturing winds from an orbiting star, or by a gas cloud that spiraled into the black hole. The increase in the rate of material falling towards the black hole is thought to drive an X-ray brightening of a relativistic jet.
The cause of the outburst in 2006 is even less clear, but it could be due to a sudden release of energy, such as magnetic fields in a disk around the black hole that suddenly connect and become more powerful.
"It's important to figure out what's going on here because the accretion of matter onto these black holes is one of the most fundamental processes governing the evolution of galaxies," said Li, who presented these results at the 216th meeting of the American Astronomical Society meeting in Miami, FL.
These results imply that the feeble, but erratic behavior of the black hole in the Milky Way may be typical for present-day supermassive black holes.
Story Source:
Adapted from materials provided by Harvard-Smithsonian Center for Astrophysics.
http://www.cfa.harvard.edu/
http://www.sciencedaily.com/releases/20 ... 094902.htm
The Map Is Not The Territory, The Word Is Not The Object....
_______________________________________________________________
_______________________________________________________________
Fri May 28, 2010 6:42 pm » by Kingz
NASA's Swift Survey Finds 'Smoking Gun' of Black Hole Activation
ScienceDaily (May 27, 2010)
Data from an ongoing survey by NASA's Swift satellite have helped astronomers solve a decades-long mystery about why a small percentage of black holes emit vast amounts of energy.
The optical counterparts of many active galactic nuclei (circled) detected by the Swift BAT Hard X-ray Survey clearly show galaxies in the process of merging. These images, taken with the 2.1-meter telescope at Kitt Peak National Observatory in Arizona, show galaxy shapes that are either physically intertwined or distorted by the gravity of nearby neighbors. These AGN were known prior to the Swift survey, but Swift has found dozens of new ones in more distant galaxies. (Credit: NASA/Swift/NOAO/Michael Koss and Richard Mushotzky (Univ. of Maryland))
Only about one percent of supermassive black holes exhibit this behavior. The new findings confirm that black holes "light up" when galaxies collide, and the data may offer insight into the future behavior of the black hole in our own Milky Way galaxy. The study will appear in the June 20 issue of The Astrophysical Journal Letters.
The intense emission from galaxy centers, or nuclei, arises near a supermassive black hole containing between a million and a billion times the sun's mass. Giving off as much as 10 billion times the sun's energy, some of these active galactic nuclei (AGN) are the most luminous objects in the universe. They include quasars and blazars.
"Theorists have shown that the violence in galaxy mergers can feed a galaxy's central black hole," said Michael Koss, the study's lead author and a graduate student at the University of Maryland in College Park. "The study elegantly explains how the black holes switched on."
Until Swift's hard X-ray survey, astronomers never could be sure they had counted the majority of the AGN. Thick clouds of dust and gas surround the black hole in an active galaxy, which can block ultraviolet, optical and low-energy, or soft X-ray, light. Infrared radiation from warm dust near the black hole can pass through the material, but it can be confused with emissions from the galaxy's star-forming regions. Hard X-rays can help scientists directly detect the energetic black hole.
Since 2004, the Burst Alert Telescope (BAT) aboard Swift has been mapping the sky using hard X-rays.
"Building up its exposure year after year, the Swift BAT Hard X-ray Survey is the largest, most sensitive and complete census of the sky at these energies," said Neil Gehrels, Swift's principal investigator at NASA's Goddard Space Flight Center in Greenbelt, Md.
The survey, which is sensitive to AGN as far as 650 million light-years away, uncovered dozens of previously unrecognized systems.
"The Swift BAT survey is giving us a very different picture of AGN," Koss said. The team finds that about a quarter of the BAT galaxies are in mergers or close pairs. "Perhaps 60 percent of these galaxies will completely merge in the next billion years. We think we have the 'smoking gun' for merger-triggered AGN that theorists have predicted."
Other members of the study team include Richard Mushotzky and Sylvain Veilleux at the University of Maryland and Lisa Winter at the Center for Astrophysics and Space Astronomy at the University of Colorado in Boulder.
"We've never seen the onset of AGN activity so clearly," said Joel Bregman, an astronomer at the University Michigan, Ann Arbor, who was not involved in the study. "The Swift team must be identifying an early stage of the process with the Hard X-ray Survey."
Swift, launched in November 2004, is managed by Goddard. It was built and is being operated in collaboration with Penn State, the Los Alamos National Laboratory in New Mexico, and General Dynamics in Falls Church, Va.; the University of Leicester and Mullard Space Sciences Laboratory in the United Kingdom; Brera Observatory and the Italian Space Agency in Italy; plus additional partners in Germany and Japan.
Story Source:
Adapted from materials provided by NASA/Goddard Space Flight Center. http://www.nasa.gov/centers/goddard/home/index.html
http://www.sciencedaily.com/releases/20 ... 170239.htm
ScienceDaily (May 27, 2010)
Data from an ongoing survey by NASA's Swift satellite have helped astronomers solve a decades-long mystery about why a small percentage of black holes emit vast amounts of energy.
The optical counterparts of many active galactic nuclei (circled) detected by the Swift BAT Hard X-ray Survey clearly show galaxies in the process of merging. These images, taken with the 2.1-meter telescope at Kitt Peak National Observatory in Arizona, show galaxy shapes that are either physically intertwined or distorted by the gravity of nearby neighbors. These AGN were known prior to the Swift survey, but Swift has found dozens of new ones in more distant galaxies. (Credit: NASA/Swift/NOAO/Michael Koss and Richard Mushotzky (Univ. of Maryland))
Only about one percent of supermassive black holes exhibit this behavior. The new findings confirm that black holes "light up" when galaxies collide, and the data may offer insight into the future behavior of the black hole in our own Milky Way galaxy. The study will appear in the June 20 issue of The Astrophysical Journal Letters.
The intense emission from galaxy centers, or nuclei, arises near a supermassive black hole containing between a million and a billion times the sun's mass. Giving off as much as 10 billion times the sun's energy, some of these active galactic nuclei (AGN) are the most luminous objects in the universe. They include quasars and blazars.
"Theorists have shown that the violence in galaxy mergers can feed a galaxy's central black hole," said Michael Koss, the study's lead author and a graduate student at the University of Maryland in College Park. "The study elegantly explains how the black holes switched on."
Until Swift's hard X-ray survey, astronomers never could be sure they had counted the majority of the AGN. Thick clouds of dust and gas surround the black hole in an active galaxy, which can block ultraviolet, optical and low-energy, or soft X-ray, light. Infrared radiation from warm dust near the black hole can pass through the material, but it can be confused with emissions from the galaxy's star-forming regions. Hard X-rays can help scientists directly detect the energetic black hole.
Since 2004, the Burst Alert Telescope (BAT) aboard Swift has been mapping the sky using hard X-rays.
"Building up its exposure year after year, the Swift BAT Hard X-ray Survey is the largest, most sensitive and complete census of the sky at these energies," said Neil Gehrels, Swift's principal investigator at NASA's Goddard Space Flight Center in Greenbelt, Md.
The survey, which is sensitive to AGN as far as 650 million light-years away, uncovered dozens of previously unrecognized systems.
"The Swift BAT survey is giving us a very different picture of AGN," Koss said. The team finds that about a quarter of the BAT galaxies are in mergers or close pairs. "Perhaps 60 percent of these galaxies will completely merge in the next billion years. We think we have the 'smoking gun' for merger-triggered AGN that theorists have predicted."
Other members of the study team include Richard Mushotzky and Sylvain Veilleux at the University of Maryland and Lisa Winter at the Center for Astrophysics and Space Astronomy at the University of Colorado in Boulder.
"We've never seen the onset of AGN activity so clearly," said Joel Bregman, an astronomer at the University Michigan, Ann Arbor, who was not involved in the study. "The Swift team must be identifying an early stage of the process with the Hard X-ray Survey."
Swift, launched in November 2004, is managed by Goddard. It was built and is being operated in collaboration with Penn State, the Los Alamos National Laboratory in New Mexico, and General Dynamics in Falls Church, Va.; the University of Leicester and Mullard Space Sciences Laboratory in the United Kingdom; Brera Observatory and the Italian Space Agency in Italy; plus additional partners in Germany and Japan.
Story Source:
Adapted from materials provided by NASA/Goddard Space Flight Center. http://www.nasa.gov/centers/goddard/home/index.html
http://www.sciencedaily.com/releases/20 ... 170239.htm
The Map Is Not The Territory, The Word Is Not The Object....
_______________________________________________________________
_______________________________________________________________
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