Hubble directly observes the disk around a black hole

ScienceDaily (Nov. 4, 2011) — A team of scientists has used the NASA/ESA Hubble Space Telescope to observe a quasar accretion disc -- a brightly glowing disc of matter that is slowly being sucked into its galaxy's central black hole. Their study makes use of a novel technique that uses gravitational lensing to give an immense boost to the power of the telescope. The incredible precision of the method has allowed astronomers to directly measure the disc's size and plot the temperature across different parts of the disc.

An international team of astronomers has used a new technique to study the bright disc of matter surrounding a faraway black hole. Using the NASA/ESA Hubble Space Telescope, combined with the gravitational lensing effect of stars in a distant galaxy [1], the team measured the disc's size and studied the colours (and hence the temperatures) of different parts of the disc. These observations show a level of precision equivalent to spotting individual grains of sand on the surface of the Moon.

While black holes themselves are invisible, the forces they unleash cause some of the brightest phenomena in the Universe. Quasars -- short for quasi-stellar objects -- are glowing discs of matter that orbit supermassive black holes, heating up and emitting extremely bright radiation as they do so.

"A quasar accretion disc has a typical size of a few light-days, or around 100 billion kilometres across, but they lie billions of light-years away. This means their apparent size when viewed from Earth is so small that we will probably never have a telescope powerful enough to see their structure directly," explains Jose Muñoz, the lead scientist in this study.

Until now, the minute apparent size of quasars has meant that most of our knowledge of their inner structure has been based on theoretical extrapolations, rather than direct observations.

The team therefore used an innovative method to study the quasar: using the stars in an intervening galaxy as a scanning microscope to probe features in the quasar's disc that would otherwise be far too small to see. As these stars move across the light from the quasar, gravitational effects amplify the light from different parts of the quasar, giving detailed colour information for a line that crosses through the accretion disc.

The team observed a group of distant quasars that are gravitationally lensed by the chance alignment of other galaxies in the foreground, producing several images of the quasar.

They spotted subtle differences in colour between the images, and changes in colour over the time the observations were carried out. Part of these colour differences are caused by the properties of dust in the intervening galaxies: the light coming from each one of the lensed images has followed a different path through the galaxy, so that the various colours encapsulate information about the material within the galaxy. Measuring the way and extent to which the dust within the galaxies blocks light (known to astronomers as the extinction law) at such distances is itself an important result in the study.

For one of the quasars they studied, though, there were clear signs that stars in the intervening galaxy were passing through the path of the light from the quasar [2]. Just as the gravitational effect due to the whole intervening galaxy can bend and amplify the quasar's light, so can that of the stars within the intervening galaxy subtly bend and amplify the light from different parts of the accretion disc as they pass through the path of the quasar's light.

By recording the variation in colour, the team were able to reconstruct the colour profile across the accretion disc. This is important because the temperature of an accretion disc increases the closer it is to the black hole, and the colours emitted by the hot matter get bluer the hotter they are. This allowed the team to measure the diameter of the disc of hot matter, and plot how hot it is at different distances from the centre.

They found that the disc is between four and eleven light-days across (approximately 100 to 300 billion kilometres). While this measurement shows large uncertainties, it is still a remarkably accurate measurement for a small object at such a great distance, and the method holds great potential for increased accuracy in the future.

"This result is very relevant because it implies we are now able to obtain observational data on the structure of these systems, rather than relying on theory alone," says Muñoz. "Quasars' physical properties are not yet well understood. This new ability to obtain observational measurements is therefore opening a new window to help understand the nature of these objects."

Notes:

1] Gravity bends the structure of spacetime, and hence deflects beams of light. When the alignment is right, with one object directly behind another, the foreground object's gravity 'bends' the light like a lens, a process called gravitational lensing. Gravitational lenses typically produce multiple, distorted images of the distant object.

The most dramatic effects from gravitational lensing are the amplification and distortion of light from distant galaxies as it passes through massive galaxy clusters.

This effect also takes place on smaller scales, with galaxies at an intermediate distance lensing the light of distant quasars, producing multiple images of them that are visible through the lens galaxy.

Individual stars can also lens light, although this effect, called gravitational microlensing, is much more subtle and can only be detected by measuring how the lensing effect increases the source's brightness.

This study makes use of gravitational microlensing by stars in a foreground galaxy to study the accretion disc of a quasar in the background. It also uses the interplay of quasar light and gravitational lensing to probe the gas and dust content of intermediate galaxies.

[2] The lens galaxy in which this phenomenon was observed is called [WKK93] G; the lensed quasar is called HE 1104-1805.

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Journal Reference:

J.A. Mun ~oz, E. Mediavilla, C.S. Kochanek, E.E. Falco and A.M. Mosquera. A Study of Gravitational Lens Chromaticity with the Hubble Space Telescope. Astrophysical Journal, December 1, 2011

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Disclaimer: Views expressed in this article do not necessarily reflect those of ScienceDaily or its staff.

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Hubble directly observes the disk around a black hole

ScienceDaily (Nov. 4, 2011) — A team of scientists has used the NASA/ESA Hubble Space Telescope to observe a quasar accretion disc -- a brightly glowing disc of matter that is slowly being sucked into its galaxy's central black hole. Their study makes use of a novel technique that uses gravitational lensing to give an immense boost to the power of the telescope. The incredible precision of the method has allowed astronomers to directly measure the disc's size and plot the temperature across different parts of the disc.

An international team of astronomers has used a new technique to study the bright disc of matter surrounding a faraway black hole. Using the NASA/ESA Hubble Space Telescope, combined with the gravitational lensing effect of stars in a distant galaxy [1], the team measured the disc's size and studied the colours (and hence the temperatures) of different parts of the disc. These observations show a level of precision equivalent to spotting individual grains of sand on the surface of the Moon.

While black holes themselves are invisible, the forces they unleash cause some of the brightest phenomena in the Universe. Quasars -- short for quasi-stellar objects -- are glowing discs of matter that orbit supermassive black holes, heating up and emitting extremely bright radiation as they do so.

"A quasar accretion disc has a typical size of a few light-days, or around 100 billion kilometres across, but they lie billions of light-years away. This means their apparent size when viewed from Earth is so small that we will probably never have a telescope powerful enough to see their structure directly," explains Jose Muñoz, the lead scientist in this study.

Until now, the minute apparent size of quasars has meant that most of our knowledge of their inner structure has been based on theoretical extrapolations, rather than direct observations.

The team therefore used an innovative method to study the quasar: using the stars in an intervening galaxy as a scanning microscope to probe features in the quasar's disc that would otherwise be far too small to see. As these stars move across the light from the quasar, gravitational effects amplify the light from different parts of the quasar, giving detailed colour information for a line that crosses through the accretion disc.

The team observed a group of distant quasars that are gravitationally lensed by the chance alignment of other galaxies in the foreground, producing several images of the quasar.

They spotted subtle differences in colour between the images, and changes in colour over the time the observations were carried out. Part of these colour differences are caused by the properties of dust in the intervening galaxies: the light coming from each one of the lensed images has followed a different path through the galaxy, so that the various colours encapsulate information about the material within the galaxy. Measuring the way and extent to which the dust within the galaxies blocks light (known to astronomers as the extinction law) at such distances is itself an important result in the study.

For one of the quasars they studied, though, there were clear signs that stars in the intervening galaxy were passing through the path of the light from the quasar [2]. Just as the gravitational effect due to the whole intervening galaxy can bend and amplify the quasar's light, so can that of the stars within the intervening galaxy subtly bend and amplify the light from different parts of the accretion disc as they pass through the path of the quasar's light.

By recording the variation in colour, the team were able to reconstruct the colour profile across the accretion disc. This is important because the temperature of an accretion disc increases the closer it is to the black hole, and the colours emitted by the hot matter get bluer the hotter they are. This allowed the team to measure the diameter of the disc of hot matter, and plot how hot it is at different distances from the centre.

They found that the disc is between four and eleven light-days across (approximately 100 to 300 billion kilometres). While this measurement shows large uncertainties, it is still a remarkably accurate measurement for a small object at such a great distance, and the method holds great potential for increased accuracy in the future.

"This result is very relevant because it implies we are now able to obtain observational data on the structure of these systems, rather than relying on theory alone," says Muñoz. "Quasars' physical properties are not yet well understood. This new ability to obtain observational measurements is therefore opening a new window to help understand the nature of these objects."

Notes:

1] Gravity bends the structure of spacetime, and hence deflects beams of light. When the alignment is right, with one object directly behind another, the foreground object's gravity 'bends' the light like a lens, a process called gravitational lensing. Gravitational lenses typically produce multiple, distorted images of the distant object.

The most dramatic effects from gravitational lensing are the amplification and distortion of light from distant galaxies as it passes through massive galaxy clusters.

This effect also takes place on smaller scales, with galaxies at an intermediate distance lensing the light of distant quasars, producing multiple images of them that are visible through the lens galaxy.

Individual stars can also lens light, although this effect, called gravitational microlensing, is much more subtle and can only be detected by measuring how the lensing effect increases the source's brightness.

This study makes use of gravitational microlensing by stars in a foreground galaxy to study the accretion disc of a quasar in the background. It also uses the interplay of quasar light and gravitational lensing to probe the gas and dust content of intermediate galaxies.

[2] The lens galaxy in which this phenomenon was observed is called [WKK93] G; the lensed quasar is called HE 1104-1805.

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Note: Materials may be edited for content and length. For further information, please contact the source cited above.

Journal Reference:

J.A. Mun ~oz, E. Mediavilla, C.S. Kochanek, E.E. Falco and A.M. Mosquera. A Study of Gravitational Lens Chromaticity with the Hubble Space Telescope. Astrophysical Journal, December 1, 2011

Note: If no author is given, the source is cited instead.

Disclaimer: Views expressed in this article do not necessarily reflect those of ScienceDaily or its staff.

View the original article here

Planets smashed into dust near supermassive black holes

ScienceDaily (Oct. 28, 2011) — Fat doughnut-shaped dust shrouds that obscure about half of supermassive black holes could be the result of high speed crashes between planets and asteroids, according to a new theory from an international team of astronomers.

The scientists, led by Dr. Sergei Nayakshin of the University of Leicester, are publishing their results in the journal Monthly Notices of the Royal Astronomical Society.

Supermassive black holes reside in the central parts of most galaxies. Observations indicate that about 50% of them are hidden from view by mysterious clouds of dust, the origin of which is not completely understood. The new theory is inspired by our own Solar System, where the so-called zodiacal dust is known to originate from collisions between solid bodies such as asteroids and comets. The scientists propose that the central regions of galaxies contain not only black holes and stars but also planets and asteroids.

Collisions between these rocky objects would occur at colossal speeds as large as 1000 km per second, continuously shattering and fragmenting the objects, until eventually they end up as microscopic dust. Dr. Nayakshin points out that this harsh environment -- radiation and frequent collisions -- would make the planets orbiting supermassive black holes sterile, even before they are destroyed. "Too bad for life on these planets," he says, "but on the other hand the dust created in this way blocks much of the harmful radiation from reaching the rest of the host galaxy. This in turn may make it easier for life to prosper elsewhere in the rest of the central region of the galaxy."

He also believes that understanding the origin of the dust near black holes is important in our models of how these monsters grow and how exactly they affect their host galaxies. "We suspect that the supermassive black hole in our own Galaxy, the Milky Way, expelled most of the gas that would otherwise turn into more stars and planets," he continues, "Understanding the origin of the dust in the inner regions of galaxies would take us one step closer to solving the mystery of the supermassive black holes."

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Journal Reference:

Sergei Nayakshin, Sergey Sazonov, Rashid Sunyaev. Are SMBHs shrouded by 'super-Oort' clouds of comets and asteroids? Monthly Notices of the Royal Astronomical Society, 2011; (submitted) [link]

Note: If no author is given, the source is cited instead.

Disclaimer: Views expressed in this article do not necessarily reflect those of ScienceDaily or its staff.

View the original article here

Planets smashed into dust near supermassive black holes

ScienceDaily (Oct. 28, 2011) — Fat doughnut-shaped dust shrouds that obscure about half of supermassive black holes could be the result of high speed crashes between planets and asteroids, according to a new theory from an international team of astronomers.

The scientists, led by Dr. Sergei Nayakshin of the University of Leicester, are publishing their results in the journal Monthly Notices of the Royal Astronomical Society.

Supermassive black holes reside in the central parts of most galaxies. Observations indicate that about 50% of them are hidden from view by mysterious clouds of dust, the origin of which is not completely understood. The new theory is inspired by our own Solar System, where the so-called zodiacal dust is known to originate from collisions between solid bodies such as asteroids and comets. The scientists propose that the central regions of galaxies contain not only black holes and stars but also planets and asteroids.

Collisions between these rocky objects would occur at colossal speeds as large as 1000 km per second, continuously shattering and fragmenting the objects, until eventually they end up as microscopic dust. Dr. Nayakshin points out that this harsh environment -- radiation and frequent collisions -- would make the planets orbiting supermassive black holes sterile, even before they are destroyed. "Too bad for life on these planets," he says, "but on the other hand the dust created in this way blocks much of the harmful radiation from reaching the rest of the host galaxy. This in turn may make it easier for life to prosper elsewhere in the rest of the central region of the galaxy."

He also believes that understanding the origin of the dust near black holes is important in our models of how these monsters grow and how exactly they affect their host galaxies. "We suspect that the supermassive black hole in our own Galaxy, the Milky Way, expelled most of the gas that would otherwise turn into more stars and planets," he continues, "Understanding the origin of the dust in the inner regions of galaxies would take us one step closer to solving the mystery of the supermassive black holes."

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The above story is reprinted from materials provided by Royal Astronomical Society (RAS).

Note: Materials may be edited for content and length. For further information, please contact the source cited above.

Journal Reference:

Sergei Nayakshin, Sergey Sazonov, Rashid Sunyaev. Are SMBHs shrouded by 'super-Oort' clouds of comets and asteroids? Monthly Notices of the Royal Astronomical Society, 2011; (submitted) [link]

Note: If no author is given, the source is cited instead.

Disclaimer: Views expressed in this article do not necessarily reflect those of ScienceDaily or its staff.

View the original article here

Astrophysicists find evidence of black holes' destruction of stars

ScienceDaily (Oct. 12, 2011) — Astrophysicists have found evidence of black holes destroying stars, a long-sought phenomenon that provides a new window into general relativity. The research, reported in the latest issue of the Astrophysical Journal, also opens up a method to search for the possible existence of a large population of presently undetectable "intermediate mass" black holes which are hypothesized to be precursors to the super-massive black holes at the centers of most large galaxies.

The study was carried out primarily by Glennys Farrar and Sjoert van Velzen at New York University's Center for Cosmology and Particle Physics, and also included the following researchers: Suvi Gezari of Johns Hopkins University's Department of Physics and Astronomy; Linda Ostman of Spain's Universitat Autònoma de Barcelona; Nidia Morrell of the Las Campanas Observatory in Chile; Dennis Zaritsky of the University of Arizona; Matthew Smith of South Africa's University of Cape Town; Joseph Gelfand of NYU-Abu Dhabi; and Andrew Drake of Caltech. Van Velzen is currently a doctoral candidate at Radboud University in the Netherlands.

Cosmologists have calculated that, on occasion, a star's orbit will be disturbed in such a way that it passes very near the super-massive black hole at the center of its galaxy -- but not so close that it is captured whole. Such a star will be torn apart by the extreme tidal forces it experiences: the force of gravity on the near side of the star is so much stronger than that on the far side that the gravitational force holding the star together is overwhelmed, causing the star to simply come apart. While some of the star's matter falls into the black hole, much of it continues in chaotic orbits, crashing into itself and producing intense radiation lasting days to months. These phenomena are called stellar tidal disruption flares, or TDFs.

Although discovering evidence of TDFs has been a high priority of astrophysicists for many years, and several possible examples have been found using X-ray and UV satellites, discovering TDFs in a large-scale, systematic survey using ground-based optical telescopes as has now been achieved, is critical to controlling bias and avoiding misidentifications.

The difficulty in detecting TDFs is largely due to the challenge of distinguishing them from more common types of flares such as supernovae. (For every TDF there are about 1000 supernovae.) In addition, some super-massive black holes have an "accretion disk" surrounding them -- gas and dust, often left from an earlier merger with another galaxy -- which is continuously feeding the hole. Such accreting black holes are usually evident from the bright emission they produce and are known as quasars or Active Galactic Nuclei (AGN). However, a hiccup in the accretion of an undetected active black hole could produce a flare that might be mistakenly identified as a TDF.

The researchers on the Astrophysical Journal study uncovered sound evidence for the presence of two TDFs through a rigorous analysis of archival data from the Sloan Digital Sky Survey (SDSS).

To do so, they sifted through voluminous SDSS data, in which more than 2 million galaxies were repeatedly observed over 10 years. By very carefully registering the images and looking at differences between consecutive images, they obtained a sample of 342 intense and well-measured flares.

Of these, almost all could be classified into supernovae and AGN flares. However, two cases were left that did not fit either classification. By relying on multi-year observations, the researchers could see that the two flares' host galaxies showed no other flaring activity, as would be the case if the flares came from a hidden variable AGN. This means the possibility these two flares were produced by undetected AGNs is extremely small.

In addition, the researchers located these flares at the nucleus of their galaxy with high precision, which reduces the likelihood that they are supernovae to less than 1 percent since supernovae are randomly distributed through galaxies.

Finally, the properties of these flares are very different from flares of AGNs and supernovae -- and their spectra are unlike any supernovae observed to date. Supernovae flares are characteristically very blue at first but become red as they cool and rapidly decay, whereas the TDF flares are very blue throughout -- slowly decaying without changing color. This behavior is consistent with expectations for a TDF -- the debris from the star should rapidly form an accretion disk and look like a short-lived AGN.

Sjoert van Velzen, the study's lead author, was a Dutch first-year graduate student who came to NYU to work under the direction of Glennys Farrar, a Professor of Physics at NYU and senior scientist of the project. Van Velzen is now completing his Ph. D. in Holland.

About his first encounter with real scientific work, van Velzen says, "Searching through 2.6 million galaxies was actually a lot of fun -- there is so much to discover! Based on our search criteria and observing two TDFs that met those criteria, the rate of TDFs is about once per 100,000 years, per galaxy. It's quite thrilling to have been able to make such a measurement."

"The next step is to develop models to explain in detail the flares' properties and duration, and address the question of whether TDFs could be responsible for producing Ultrahigh Energy Cosmic Rays, whose sources have been elusive up to now," says Farrar. "It is very exciting that we are on the verge of obtaining a large and better-observed sample of TDFs to study -- though a more sensitive search of SDSS archival data and the new generation of transient surveys which will observe more flares in real-time and with multi-wavelength follow-up. A large sample will be invaluable to understanding many outstanding questions in astrophysics."

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The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by New York University.

Journal Reference:

Sjoert van Velzen, Glennys R. Farrar, Suvi Gezari, Nidia Morrell, Dennis Zaritsky, Linda Ostman, Mathew Smith, Joseph Gelfand, Andrew J. Drake. Optical discovery of probable stellar tidal disruption flares. Astrophysical Journal, 2011 (in press) [link]

Note: If no author is given, the source is cited instead.

Disclaimer: Views expressed in this article do not necessarily reflect those of ScienceDaily or its staff.

View the original article here

Astrophysicists find evidence of black holes' destruction of stars

ScienceDaily (Oct. 12, 2011) — Astrophysicists have found evidence of black holes destroying stars, a long-sought phenomenon that provides a new window into general relativity. The research, reported in the latest issue of the Astrophysical Journal, also opens up a method to search for the possible existence of a large population of presently undetectable "intermediate mass" black holes which are hypothesized to be precursors to the super-massive black holes at the centers of most large galaxies.

The study was carried out primarily by Glennys Farrar and Sjoert van Velzen at New York University's Center for Cosmology and Particle Physics, and also included the following researchers: Suvi Gezari of Johns Hopkins University's Department of Physics and Astronomy; Linda Ostman of Spain's Universitat Autònoma de Barcelona; Nidia Morrell of the Las Campanas Observatory in Chile; Dennis Zaritsky of the University of Arizona; Matthew Smith of South Africa's University of Cape Town; Joseph Gelfand of NYU-Abu Dhabi; and Andrew Drake of Caltech. Van Velzen is currently a doctoral candidate at Radboud University in the Netherlands.

Cosmologists have calculated that, on occasion, a star's orbit will be disturbed in such a way that it passes very near the super-massive black hole at the center of its galaxy -- but not so close that it is captured whole. Such a star will be torn apart by the extreme tidal forces it experiences: the force of gravity on the near side of the star is so much stronger than that on the far side that the gravitational force holding the star together is overwhelmed, causing the star to simply come apart. While some of the star's matter falls into the black hole, much of it continues in chaotic orbits, crashing into itself and producing intense radiation lasting days to months. These phenomena are called stellar tidal disruption flares, or TDFs.

Although discovering evidence of TDFs has been a high priority of astrophysicists for many years, and several possible examples have been found using X-ray and UV satellites, discovering TDFs in a large-scale, systematic survey using ground-based optical telescopes as has now been achieved, is critical to controlling bias and avoiding misidentifications.

The difficulty in detecting TDFs is largely due to the challenge of distinguishing them from more common types of flares such as supernovae. (For every TDF there are about 1000 supernovae.) In addition, some super-massive black holes have an "accretion disk" surrounding them -- gas and dust, often left from an earlier merger with another galaxy -- which is continuously feeding the hole. Such accreting black holes are usually evident from the bright emission they produce and are known as quasars or Active Galactic Nuclei (AGN). However, a hiccup in the accretion of an undetected active black hole could produce a flare that might be mistakenly identified as a TDF.

The researchers on the Astrophysical Journal study uncovered sound evidence for the presence of two TDFs through a rigorous analysis of archival data from the Sloan Digital Sky Survey (SDSS).

To do so, they sifted through voluminous SDSS data, in which more than 2 million galaxies were repeatedly observed over 10 years. By very carefully registering the images and looking at differences between consecutive images, they obtained a sample of 342 intense and well-measured flares.

Of these, almost all could be classified into supernovae and AGN flares. However, two cases were left that did not fit either classification. By relying on multi-year observations, the researchers could see that the two flares' host galaxies showed no other flaring activity, as would be the case if the flares came from a hidden variable AGN. This means the possibility these two flares were produced by undetected AGNs is extremely small.

In addition, the researchers located these flares at the nucleus of their galaxy with high precision, which reduces the likelihood that they are supernovae to less than 1 percent since supernovae are randomly distributed through galaxies.

Finally, the properties of these flares are very different from flares of AGNs and supernovae -- and their spectra are unlike any supernovae observed to date. Supernovae flares are characteristically very blue at first but become red as they cool and rapidly decay, whereas the TDF flares are very blue throughout -- slowly decaying without changing color. This behavior is consistent with expectations for a TDF -- the debris from the star should rapidly form an accretion disk and look like a short-lived AGN.

Sjoert van Velzen, the study's lead author, was a Dutch first-year graduate student who came to NYU to work under the direction of Glennys Farrar, a Professor of Physics at NYU and senior scientist of the project. Van Velzen is now completing his Ph. D. in Holland.

About his first encounter with real scientific work, van Velzen says, "Searching through 2.6 million galaxies was actually a lot of fun -- there is so much to discover! Based on our search criteria and observing two TDFs that met those criteria, the rate of TDFs is about once per 100,000 years, per galaxy. It's quite thrilling to have been able to make such a measurement."

"The next step is to develop models to explain in detail the flares' properties and duration, and address the question of whether TDFs could be responsible for producing Ultrahigh Energy Cosmic Rays, whose sources have been elusive up to now," says Farrar. "It is very exciting that we are on the verge of obtaining a large and better-observed sample of TDFs to study -- though a more sensitive search of SDSS archival data and the new generation of transient surveys which will observe more flares in real-time and with multi-wavelength follow-up. A large sample will be invaluable to understanding many outstanding questions in astrophysics."

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The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by New York University.

Journal Reference:

Sjoert van Velzen, Glennys R. Farrar, Suvi Gezari, Nidia Morrell, Dennis Zaritsky, Linda Ostman, Mathew Smith, Joseph Gelfand, Andrew J. Drake. Optical discovery of probable stellar tidal disruption flares. Astrophysical Journal, 2011 (in press) [link]

Note: If no author is given, the source is cited instead.

Disclaimer: Views expressed in this article do not necessarily reflect those of ScienceDaily or its staff.

View the original article here

Space telescopes reveal secrets of turbulent black hole

ScienceDaily (Sep. 30, 2011) — Supermassive black holes at the hearts of active galaxies swallow large amounts of gas. During this feast they spill a lot of their 'food', which is discharged in turbulent outbursts. An international team of astronomers has revealed some striking features of such an outburst around a supermassive black hole in a distant galaxy. They found a very hot 'convertor' corona hovering above the black hole and cold gas 'bullets' in hotter diffuse gas, speeding outwards with velocities up to 700 km/s.

Unlike popular belief, not all the matter around a black hole is swallowed up. A disc of infalling gas forms around the black hole. On the journey inwards the gas and dust emit large amounts of X-ray and UV radiation. This radiation can be so strong that it diverts a part of the gas inflow. It causes winds flowing outward with velocities up to several hundreds of km/s. An international team of astronomers led by Dr. Jelle Kaastra from the SRON Netherlands Institute for Space Research took the opportunity to observe and map such an extreme environment around one of the brightest supermassive black holes known to us. This 'monster' black hole -- in the distant galaxy Markarian 509 -- has a mass 300 million times that of the Sun.

Convertor corona

The Markarian 509 black hole is surrounded by a disc of gas shining bright in ultraviolet light. This emission varies in a synchronised way with emissions observed at the low end of the X-ray band, some 100s of times higher in energy than visible light. "The only way to explain this is by having gas hotter than that in the disc, a so-called 'corona', hovering above the disc," Jelle Kaastra says. "This corona absorbs and reprocesses the ultraviolet light from the disc, energising it and converting it into X-ray light. It must have a temperature of a few million degrees. Using five space telescopes, which enabled us to observe the area in unprecedented detail, we actually discovered a very hot 'corona' of gas hovering above the disc. This discovery allows us to make sense of some of the observations of active galaxies that have been hard to explain so far."

Cold gas bullets

The X-ray spectrum obtained with the Reflection Grating Spectrometer (RGS) of the space telescope XMM-Newton is the best obtained so far of such a system. It reveals unprecedented details of its gaseous environment. For the first time it has been possible to show that the outflow consists of at least five distinct components with temperatures ranging between 20.000 to a million degrees. The superb ultraviolet spectrum obtained by the Cosmic Origins Spectrograph of the Hubble Space Telescope reveals that the coolest gas in the line of sight towards Markarian 509 has 14 different velocity components at various locations in the innermost parts of this galaxy. Thus far only seven velocity components were identified.

The combined X-ray and UV measurements demonstrate that most of the visible outflowing gas is blown off from a dusty gas torus surrounding the central region more than 15 light years away from the black hole. This outflow consists of dense, cold blobs or gas bullets embedded in hotter diffuse gas. "Even at a distance of 15 light years, the energy released near the black hole manages to blow off gas from the dusty torus that surrounds the disc of infalling gas," Kaastra says.

Signs of cosmic collision

Further outwards, the signatures of the interstellar gas of the host galaxy are seen. That gas is strongly ionised by the central X-ray source: atoms are stripped of some or most of their electrons when illuminated by the powerful flux of X-rays. Even further out, at hundred thousands of light years, the X-ray light shines through gas falling in towards Markarian 509 with speeds of 200 km/s. This gas may point at a collision with a smaller galaxy in the past, that may have triggered the activity of Markarian 509.

Space telescopes

Five large space telescopes were involved in this hundred days campaign that took place in late 2009. The heart of the campaign consisted of repeated visible, X-ray and gamma-ray observations with ESA's XMM-Newton and INTEGRAL satellites, which monitored Markarian 509 for six weeks. This was followed by long observations with NASA's Chandra X-ray satellite, using the Low Energy Transmission Grating, and the NASA/ESA Hubble Space Telescope using the new Cosmic Origins Spectrograph. Prior to these observations short snapshots to monitor the behaviour of the source at all wavelengths were taken with the Swift satellite.

The combined efforts of all these instruments and astronomers gave an unprecedented insight into the core of an active galaxy. Right in the middle of the campaign the source went into outburst. The physical changes due to this outburst could be followed over the electromagnetic spectrum from visible light to X-rays.

Papers

The international consortium responsible for this campaign consists of 26 astronomers from 21 institutes on 4 continents. The first results of this campaign will be published as a series of 7 papers in Astronomy and Astrophysics, titled Multiwavelength campaign on Mrk 509 (see below). More results are in preparation.

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The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by SRON Netherlands Institute for Space Research.

Journal References:

J. S. Kaastra, P.-O. Petrucci, M. Cappi, N. Arav, E. Behar, S. Bianchi, J. Bloom, A. J. Blustin, G. Branduardi-Raymont, E. Costantini, M. Dadina, R. G. Detmers, J. Ebrero, P. G. Jonker, C. Klein, G. A. Kriss, P. Lubinski, J. Malzac, M. Mehdipour, S. Paltani, C. Pinto, G. Ponti, E. M. Ratti, R. A. N. Smith, K. C. Steenbrugge, C. P. de Vries. Multiwavelength campaign on Mrk 509: I. Variability and spectral energy distribution. Astronomy & Astrophysics, 2011; 534: A36 DOI: 10.1051/0004-6361/201116869J. S. Kaastra, C. P. de Vries, K. C. Steenbrugge, R. G. Detmers, J. Ebrero, E. Behar, S. Bianchi, E. Costantini, G. A. Kriss, M. Mehdipour, S. Paltani, P.-O. Petrucci, C. Pinto, G. Ponti. Multiwavelength campaign on Mrk 509: II. Analysis of high-quality Reflection Grating Spectrometer spectra. Astronomy & Astrophysics, 2011; 534: A37 DOI: 10.1051/0004-6361/201116870R. G. Detmers, J. S. Kaastra, K. C. Steenbrugge, J. Ebrero, G. A. Kriss, N. Arav, E. Behar, E. Costantini, G. Branduardi-Raymont, M. Mehdipour, S. Bianchi, M. Cappi, P. Petrucci, G. Ponti, C. Pinto, E. M. Ratti, T. Holczer. Multiwavelength campaign on Mrk 509: III. The 600 ks RGS spectrum: unravelling the inner region of an AGN. Astronomy & Astrophysics, 2011; 534: A38 DOI: 10.1051/0004-6361/201116899M. Mehdipour, G. Branduardi-Raymont, J. S. Kaastra, P. O. Petrucci, G. A. Kriss, G. Ponti, A. J. Blustin, S. Paltani, M. Cappi, R. G. Detmers, K. C. Steenbrugge. Multiwavelength campaign on Mrk 509: IV. Optical-UV-X-ray variability and the nature of the soft X-ray excess. Astronomy & Astrophysics, 2011; 534: A39 DOI: 10.1051/0004-6361/201116875J. Ebrero, G. A. Kriss, J. S. Kaastra, R. G. Detmers, K. C. Steenbrugge, E. Costantini, N. Arav, S. Bianchi, M. Cappi, G. Branduardi-Raymont, M. Mehdipour, P. O. Petrucci, C. Pinto, G. Ponti. Multiwavelength campaign on Mrk 509: V. Chandra-LETGS observation of the ionized absorber. Astronomy & Astrophysics, 2011; 534: A40 DOI: 10.1051/0004-6361/201117067G. A. Kriss, N. Arav, J. S. Kaastra, J. Ebrero, C. Pinto, B. Borguet, D. Edmonds, E. Costantini, K. C. Steenbrugge, R. G. Detmers, E. Behar, S. Bianchi, A. J. Blustin, G. Branduardi-Raymont, M. Cappi, M. Mehdipour, P. Petrucci, G. Ponti. Multiwavelength campaign on Mrk 509: VI. HST/COS observations of the far-ultraviolet spectrum. Astronomy & Astrophysics, 2011; 534: A41 DOI: 10.1051/0004-6361/201117123K. C. Steenbrugge, J. S. Kaastra, R. G. Detmers, J. Ebrero, G. Ponti, E. Costantini, G. A. Kriss, M. Mehdipour, C. Pinto, G. Branduardi-Raymont, E. Behar, N. Arav, M. Cappi, S. Bianchi, P.-O. Petrucci, E. M. Ratti, T. Holczer. Multiwavelength campaign on Mrk 509: VII. Relative abundances of the warm absorber. Astronomy & Astrophysics, 2011; 534: A42 DOI: 10.1051/0004-6361/201117304

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Cosmic weight watching reveals black hole-galaxy history

ScienceDaily (Sep. 29, 2011) — Using state-of-the-art technology and sophisticated data analysis tools, a team of astronomers from the Max Planck Institute for Astronomy has developed a new and powerful technique to directly determine the mass of an active galaxy at a distance of nearly 9 billion light-years from Earth. This pioneering method promises a new approach for studying the co-evolution of galaxies and their central black holes. First results indicate that for galaxies, the best part of cosmic history was not a time of sweeping changes.

One of the most intriguing developments in astronomy over the last few decades is the realization that not only do most galaxies contain central black holes of gigantic size, but also that the mass of these central black holes are directly related to the mass of their host galaxies. This correlation is predicted by the current standard model of galaxy evolution, the so-called hierarchical model, as astronomers from the Max Planck Institute for Astronomy have recently shown.

When astronomers look out to greater and greater distances, they look further and further into the past. Investigating this black hole-galaxy mass correlation at different distances, and thus at different times in cosmic history, allows astronomers to study galaxy and black hole evolution in action.

For galaxies further away than 5 billion light-years (corresponding to a redshift of z > 0.5), such studies face considerable difficulties. The typical objects of study are so-called active galaxies, and there are well-established methods to estimate the mass of such a galaxy's central black hole. It is the galaxy's mass itself that is the challenge: At such distances, standard methods of estimating a galaxy's mass become exceedingly uncertain or fail altogether.

Now, a team of astronomers from the Max Planck Institute for Astronomy, led by Dr Katherine Inskip, has, for the first time, succeeded in directly "weighing" both a galaxy and its central black hole at such a great distance using a sophisticated and novel method. The galaxy, known to astronomers by the number J090543.56+043347.3 (which encodes the galaxy's position in the sky) has a distance of 8.8 billion light-years from Earth (redshift z = 1.3).

The astronomers succeeded in measuring directly the so-called dynamical mass of this active galaxy. The key idea is the following: A galaxy's stars and gas clouds orbit the galactic centre; for instance, our Sun orbits the centre of the Milky Way galaxy once every 250 million years. The stars' different orbital speeds are a direct function of the galaxy's mass distribution. Determine orbital speeds and you can determine the galaxy's total mass.

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The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by Max-Planck-Gesellschaft.

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K. J. Inskip, K. Jahnke, H.-W. Rix, G. van de Ven. Resolving the Dynamical Mass of a z ~ 1.3 Quasi-stellar Object Host Galaxy Using SINFONI and Laser Guide Star Assisted Adaptive Optics. The Astrophysical Journal, 2011; 739 (2): 90 DOI: 10.1088/0004-637X/739/2/90

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Disclaimer: Views expressed in this article do not necessarily reflect those of ScienceDaily or its staff.

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Cosmic weight watching reveals black hole-galaxy history

ScienceDaily (Sep. 29, 2011) — Using state-of-the-art technology and sophisticated data analysis tools, a team of astronomers from the Max Planck Institute for Astronomy has developed a new and powerful technique to directly determine the mass of an active galaxy at a distance of nearly 9 billion light-years from Earth. This pioneering method promises a new approach for studying the co-evolution of galaxies and their central black holes. First results indicate that for galaxies, the best part of cosmic history was not a time of sweeping changes.

One of the most intriguing developments in astronomy over the last few decades is the realization that not only do most galaxies contain central black holes of gigantic size, but also that the mass of these central black holes are directly related to the mass of their host galaxies. This correlation is predicted by the current standard model of galaxy evolution, the so-called hierarchical model, as astronomers from the Max Planck Institute for Astronomy have recently shown.

When astronomers look out to greater and greater distances, they look further and further into the past. Investigating this black hole-galaxy mass correlation at different distances, and thus at different times in cosmic history, allows astronomers to study galaxy and black hole evolution in action.

For galaxies further away than 5 billion light-years (corresponding to a redshift of z > 0.5), such studies face considerable difficulties. The typical objects of study are so-called active galaxies, and there are well-established methods to estimate the mass of such a galaxy's central black hole. It is the galaxy's mass itself that is the challenge: At such distances, standard methods of estimating a galaxy's mass become exceedingly uncertain or fail altogether.

Now, a team of astronomers from the Max Planck Institute for Astronomy, led by Dr Katherine Inskip, has, for the first time, succeeded in directly "weighing" both a galaxy and its central black hole at such a great distance using a sophisticated and novel method. The galaxy, known to astronomers by the number J090543.56+043347.3 (which encodes the galaxy's position in the sky) has a distance of 8.8 billion light-years from Earth (redshift z = 1.3).

The astronomers succeeded in measuring directly the so-called dynamical mass of this active galaxy. The key idea is the following: A galaxy's stars and gas clouds orbit the galactic centre; for instance, our Sun orbits the centre of the Milky Way galaxy once every 250 million years. The stars' different orbital speeds are a direct function of the galaxy's mass distribution. Determine orbital speeds and you can determine the galaxy's total mass.

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The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by Max-Planck-Gesellschaft.

Journal Reference:

K. J. Inskip, K. Jahnke, H.-W. Rix, G. van de Ven. Resolving the Dynamical Mass of a z ~ 1.3 Quasi-stellar Object Host Galaxy Using SINFONI and Laser Guide Star Assisted Adaptive Optics. The Astrophysical Journal, 2011; 739 (2): 90 DOI: 10.1088/0004-637X/739/2/90

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Space telescopes reveal secrets of turbulent black hole

ScienceDaily (Sep. 30, 2011) — Supermassive black holes at the hearts of active galaxies swallow large amounts of gas. During this feast they spill a lot of their 'food', which is discharged in turbulent outbursts. An international team of astronomers has revealed some striking features of such an outburst around a supermassive black hole in a distant galaxy. They found a very hot 'convertor' corona hovering above the black hole and cold gas 'bullets' in hotter diffuse gas, speeding outwards with velocities up to 700 km/s.

Unlike popular belief, not all the matter around a black hole is swallowed up. A disc of infalling gas forms around the black hole. On the journey inwards the gas and dust emit large amounts of X-ray and UV radiation. This radiation can be so strong that it diverts a part of the gas inflow. It causes winds flowing outward with velocities up to several hundreds of km/s. An international team of astronomers led by Dr. Jelle Kaastra from the SRON Netherlands Institute for Space Research took the opportunity to observe and map such an extreme environment around one of the brightest supermassive black holes known to us. This 'monster' black hole -- in the distant galaxy Markarian 509 -- has a mass 300 million times that of the Sun.

Convertor corona

The Markarian 509 black hole is surrounded by a disc of gas shining bright in ultraviolet light. This emission varies in a synchronised way with emissions observed at the low end of the X-ray band, some 100s of times higher in energy than visible light. "The only way to explain this is by having gas hotter than that in the disc, a so-called 'corona', hovering above the disc," Jelle Kaastra says. "This corona absorbs and reprocesses the ultraviolet light from the disc, energising it and converting it into X-ray light. It must have a temperature of a few million degrees. Using five space telescopes, which enabled us to observe the area in unprecedented detail, we actually discovered a very hot 'corona' of gas hovering above the disc. This discovery allows us to make sense of some of the observations of active galaxies that have been hard to explain so far."

Cold gas bullets

The X-ray spectrum obtained with the Reflection Grating Spectrometer (RGS) of the space telescope XMM-Newton is the best obtained so far of such a system. It reveals unprecedented details of its gaseous environment. For the first time it has been possible to show that the outflow consists of at least five distinct components with temperatures ranging between 20.000 to a million degrees. The superb ultraviolet spectrum obtained by the Cosmic Origins Spectrograph of the Hubble Space Telescope reveals that the coolest gas in the line of sight towards Markarian 509 has 14 different velocity components at various locations in the innermost parts of this galaxy. Thus far only seven velocity components were identified.

The combined X-ray and UV measurements demonstrate that most of the visible outflowing gas is blown off from a dusty gas torus surrounding the central region more than 15 light years away from the black hole. This outflow consists of dense, cold blobs or gas bullets embedded in hotter diffuse gas. "Even at a distance of 15 light years, the energy released near the black hole manages to blow off gas from the dusty torus that surrounds the disc of infalling gas," Kaastra says.

Signs of cosmic collision

Further outwards, the signatures of the interstellar gas of the host galaxy are seen. That gas is strongly ionised by the central X-ray source: atoms are stripped of some or most of their electrons when illuminated by the powerful flux of X-rays. Even further out, at hundred thousands of light years, the X-ray light shines through gas falling in towards Markarian 509 with speeds of 200 km/s. This gas may point at a collision with a smaller galaxy in the past, that may have triggered the activity of Markarian 509.

Space telescopes

Five large space telescopes were involved in this hundred days campaign that took place in late 2009. The heart of the campaign consisted of repeated visible, X-ray and gamma-ray observations with ESA's XMM-Newton and INTEGRAL satellites, which monitored Markarian 509 for six weeks. This was followed by long observations with NASA's Chandra X-ray satellite, using the Low Energy Transmission Grating, and the NASA/ESA Hubble Space Telescope using the new Cosmic Origins Spectrograph. Prior to these observations short snapshots to monitor the behaviour of the source at all wavelengths were taken with the Swift satellite.

The combined efforts of all these instruments and astronomers gave an unprecedented insight into the core of an active galaxy. Right in the middle of the campaign the source went into outburst. The physical changes due to this outburst could be followed over the electromagnetic spectrum from visible light to X-rays.

Papers

The international consortium responsible for this campaign consists of 26 astronomers from 21 institutes on 4 continents. The first results of this campaign will be published as a series of 7 papers in Astronomy and Astrophysics, titled Multiwavelength campaign on Mrk 509 (see below). More results are in preparation.

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The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by SRON Netherlands Institute for Space Research.

Journal References:

J. S. Kaastra, P.-O. Petrucci, M. Cappi, N. Arav, E. Behar, S. Bianchi, J. Bloom, A. J. Blustin, G. Branduardi-Raymont, E. Costantini, M. Dadina, R. G. Detmers, J. Ebrero, P. G. Jonker, C. Klein, G. A. Kriss, P. Lubinski, J. Malzac, M. Mehdipour, S. Paltani, C. Pinto, G. Ponti, E. M. Ratti, R. A. N. Smith, K. C. Steenbrugge, C. P. de Vries. Multiwavelength campaign on Mrk 509: I. Variability and spectral energy distribution. Astronomy & Astrophysics, 2011; 534: A36 DOI: 10.1051/0004-6361/201116869J. S. Kaastra, C. P. de Vries, K. C. Steenbrugge, R. G. Detmers, J. Ebrero, E. Behar, S. Bianchi, E. Costantini, G. A. Kriss, M. Mehdipour, S. Paltani, P.-O. Petrucci, C. Pinto, G. Ponti. Multiwavelength campaign on Mrk 509: II. Analysis of high-quality Reflection Grating Spectrometer spectra. Astronomy & Astrophysics, 2011; 534: A37 DOI: 10.1051/0004-6361/201116870R. G. Detmers, J. S. Kaastra, K. C. Steenbrugge, J. Ebrero, G. A. Kriss, N. Arav, E. Behar, E. Costantini, G. Branduardi-Raymont, M. Mehdipour, S. Bianchi, M. Cappi, P. Petrucci, G. Ponti, C. Pinto, E. M. Ratti, T. Holczer. Multiwavelength campaign on Mrk 509: III. The 600 ks RGS spectrum: unravelling the inner region of an AGN. Astronomy & Astrophysics, 2011; 534: A38 DOI: 10.1051/0004-6361/201116899M. Mehdipour, G. Branduardi-Raymont, J. S. Kaastra, P. O. Petrucci, G. A. Kriss, G. Ponti, A. J. Blustin, S. Paltani, M. Cappi, R. G. Detmers, K. C. Steenbrugge. Multiwavelength campaign on Mrk 509: IV. Optical-UV-X-ray variability and the nature of the soft X-ray excess. Astronomy & Astrophysics, 2011; 534: A39 DOI: 10.1051/0004-6361/201116875J. Ebrero, G. A. Kriss, J. S. Kaastra, R. G. Detmers, K. C. Steenbrugge, E. Costantini, N. Arav, S. Bianchi, M. Cappi, G. Branduardi-Raymont, M. Mehdipour, P. O. Petrucci, C. Pinto, G. Ponti. Multiwavelength campaign on Mrk 509: V. Chandra-LETGS observation of the ionized absorber. Astronomy & Astrophysics, 2011; 534: A40 DOI: 10.1051/0004-6361/201117067G. A. Kriss, N. Arav, J. S. Kaastra, J. Ebrero, C. Pinto, B. Borguet, D. Edmonds, E. Costantini, K. C. Steenbrugge, R. G. Detmers, E. Behar, S. Bianchi, A. J. Blustin, G. Branduardi-Raymont, M. Cappi, M. Mehdipour, P. Petrucci, G. Ponti. Multiwavelength campaign on Mrk 509: VI. HST/COS observations of the far-ultraviolet spectrum. Astronomy & Astrophysics, 2011; 534: A41 DOI: 10.1051/0004-6361/201117123K. C. Steenbrugge, J. S. Kaastra, R. G. Detmers, J. Ebrero, G. Ponti, E. Costantini, G. A. Kriss, M. Mehdipour, C. Pinto, G. Branduardi-Raymont, E. Behar, N. Arav, M. Cappi, S. Bianchi, P.-O. Petrucci, E. M. Ratti, T. Holczer. Multiwavelength campaign on Mrk 509: VII. Relative abundances of the warm absorber. Astronomy & Astrophysics, 2011; 534: A42 DOI: 10.1051/0004-6361/201117304

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Escaping gravity's clutches: Information could escape from black holes after all, study suggests

ScienceDaily (Aug. 11, 2011) — New research by scientists at the University of York gives a fresh perspective on the physics of black holes. Black holes are objects in space that are so massive and compact they were described by Einstein as "bending" space. Conventional thinking asserts that black holes swallow everything that gets too close and that nothing can escape, but the study by Prof. Samuel Braunstein and Dr. Manas Patra suggests that information could escape from black holes after all.

The implications could be revolutionary, suggesting that gravity may not be a fundamental force of nature.

Prof. Braunstein says: "Our results didn't need the details of a black hole's curved space geometry. That lends support to recent proposals that space, time and even gravity itself may be emergent properties within a deeper theory. Our work subtly changes those proposals, by identifying quantum information theory as the likely candidate for the source of an emergent theory of gravity."

But quantum mechanics is the theory of light and atoms, and many physicists are skeptical that it could be used to explain the slow evaporation of black holes without incorporating the effects of gravity.

The research, which appears in the latest issue of Physical Review Letters, uses the basic tenets of quantum mechanics to give a new description of information leaking from a black hole.

Prof. Braunstein says: "Our results actually extend the predictions made by well-established techniques that rely on a detailed knowledge of space time and black hole geometry."

Dr. Patra adds: "We cannot claim to have proven that escape from a black hole is truly possible, but that is the most straight-forward interpretation of our results. Indeed, our results suggest that quantum information theory will play a key role in a future theory combining quantum mechanics and gravity."

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The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by University of York.

Journal Reference:

Samuel Braunstein, Manas Patra. Black Hole Evaporation Rates without Spacetime. Physical Review Letters, 2011; 107 (7) DOI: 10.1103/PhysRevLett.107.071302

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Gamma-ray flash came from star being eaten by massive black hole

ScienceDaily (June 16, 2011) — A bright flash of gamma rays observed March 28 by the Swift satellite may have been the death rattle of a star falling into a massive black hole and being ripped apart, according to a team of astronomers led by the University of California, Berkeley.

When the Swift Gamma Burst Mission spacecraft first detected the flash within the constellation Draco, astronomers thought it was a gamma-ray burst from a collapsing star. On March 31, however, UC Berkeley's Joshua Bloom sent out an email circular suggesting that it wasn't a typical gamma-ray burst at all, but a high-energy jet produced as a star about the size of our sun was shredded by a black hole a million times more massive.

Careful analysis of the Swift data and subsequent observations by the Hubble Space Telescope and the Chandra X-ray Observatory confirmed Bloom's initial insight. The details are published online on June 16 in Science Express, a rapid publication arm of the journal Science.

"This is truly different from any explosive event we have seen before," Bloom said.

What made this gamma-ray flare, called Sw 1644+57, stand out from a typical burst were its long duration and the fact that it appeared to come from the center of a galaxy nearly 4 billion light years away. Since most, if not all, galaxies are thought to contain a massive black hole at the center, a long-duration burst could conceivably come from the relatively slow tidal disruption of an infalling star, the astronomers said.

"This burst produced a tremendous amount of energy over a fairly long period of time, and the event is still going on more than two and a half months later," said Bloom, an associate professor of astronomy at UC Berkeley. "That's because as the black hole rips the star apart, the mass swirls around like water going down a drain, and this swirling process releases a lot of energy."

Bloom and his colleagues propose in their Science Express paper that some 10 percent of the infalling star's mass is turned into energy and irradiated as X-rays from the swirling accretion disk or as X-rays and higher energy gamma rays from a relativistic jet that punches out along the rotation axis. Earth just happened to be in the eye of the gamma-ray beam.

Bloom draws an analogy with a quasar, which is a distant galaxy that emits bright, high-energy light because of the massive black hole at its center gobbling up stars and sending out a jet of X-rays along its rotation axis. Observed from an angle, these bright emissions are called active galactic nuclei, but when observed down the axis of the jet, they're referred to as blazars.

"We argue that this must be jetted material and we're looking down the barrel," he said. "Jetting is a common phenomenon when you have accretion disks, and black holes actually prefer to make jets."

Looking back at previous observations of this region of the cosmos, Bloom and his team could find no evidence of X-ray or gamma-ray emissions, leading them to conclude that this is a "one-off event," Bloom said.

"Here, you have a black hole sitting quiescently, not gobbling up matter, and all of a sudden something sets it off," Bloom said. "This could happen in our own galaxy, where a black hole sits at the center living in quiescence, and occasionally burbles or hiccups as it swallows a little bit of gas. From a distance, it would appear dormant, until a star randomly wanders too close and is shredded."

Probable tidal disruptions of a star by a massive black hole have previously been seen at X-ray, ultraviolet and optical wavelengths, but never before at gamma-ray energies. Such random events, especially looking down the barrel of a jet, are incredibly rare, "probably once in 100 million years in any given galaxy," said Bloom. "I would be surprised if we saw another one of these anywhere in the sky in the next decade."

The astronomers suspect that the gamma-ray emissions began March 24 or 25 in the uncatalogued galaxy at a redshift of 0.3534, putting it at a distance of about 3.8 billion light years. Bloom and his colleagues estimate that the emissions will fade over the next year.

"We think this event was detected around the time it was as bright as it will ever be, and if it's really a star being ripped apart by a massive black hole, we predict that it will never happen again in this galaxy," he said.

Bloom's colleagues include UC Berkeley theoretical physicist Elliot Quataert, who models the production of jets from accretion disks, and UC Berkeley astronomers S. Bradley Cenko, Daniel A. Perley, Nathaniel R. Butler, Linda E. Strubbe, Antonino Cucchiara, Geoffrey C. Bower and Adam N. Morgan; Dimitrios Giannios and Brian D. Metzger of Princeton University; Andrew J. Levan of the University of Warwick, Coventry, United Kingdom; Nial R. Tanvir, Paul T. O' Brien, Andrew R. King and Sergei Nayakshin of the University of Leicester in the U.K.; Fabio De Colle, Enrico Ramirez-Ruiz and James Guillochon of UC Santa Cruz; William H. Lee of the Universidad Nacional Autonoma de México in Mexico City; Andrew S. Fruchter of the Space Telescope Science Institute in Baltimore, Md.; and Alexander J. van der Horst of the Universities Space Research Association in Huntsville, Ala.

Levan is first author of the companion Science Express paper, and leader of the Chandra and Hubble Space Telescope observation team.

Bloom and his laboratory are supported by grants from NASA and the National Science Foundation.

Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by University of California - Berkeley.

Journal Reference:

Joshua S. Bloom, Dimitrios Giannios, Brian D. Metzger, S. Bradley Cenko, Daniel A. Perley, Nathaniel R. Butler, Nial R. Tanvir, Andrew J. Levan, Paul T. O' Brien, Linda E. Strubbe, Fabio De Colle, Enrico Ramirez-Ruiz, William H. Lee, Sergei Nayakshin, Eliot Quataert, Andrew R. King, Antonino Cucchiara, James Guillochon, Geoffrey C. Bower, Andrew S. Fruchter, Adam N. Morgan, Alexander J. Van Der Horst. A Possible Relativistic Jetted Outburst from a Massive Black Hole Fed by a Tidally Disrupted Star. Science, 16 June 2011 DOI: 10.1126/science.1207150

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Black hole kills star and blasts 3.8 billion light year beam at Earth

ScienceDaily (June 16, 2011) — Research led by astronomers at the University of Warwick has confirmed that the flash from one of the biggest and brightest bangs yet recorded by astronomers comes from a massive black hole at the centre of a distant galaxy. The black hole appears to have ripped apart a star that wandered too close, creating a powerful beam of energy that crossed the 3.8 billion light years to Earth.

Their research was published June 16 in the Journal Science.

The high energy X-rays and gamma-rays persisted at an extremely bright level for weeks after the event, with bright flares arising when further chunks of the star fell into the black hole. The extreme brightness of this event comes from the fact that it illuminated only a small fraction of the sky, pointing a jet of light towards the Milky Way, which was detected at Earth 3.8 billion years after the star was ripped apart.

Dr Andrew Levan, lead researcher on the paper from the University of Warwick, said: "Despite the power of this the cataclysmic event we still only happen to see this event because our solar system happened to be looking right down the barrel of this jet of energy."

The new research paper clearly establishes that the source of this event -- known now as Sw 1644+57 -- is right at the heart of far away galaxy, 3.8 billion light years away, at a spot which would be in the constellation Draco.

University of Warwick researcher Dr Andrew Levan said: "The only explanation that so far fits the size, intensity, time scale, and level of fluctuation of the observed event, is that a massive black at the very centre of that galaxy has pulled in a large star and ripped it apart by tidal disruption. The spinning black hole then created the two jets one of which pointed straight to earth."

The researchers used the Hubble Space Telescope, Swift satellite and the Chandra X-ray Observatory to study the blast. Swift's Burst Alert Telescope first discovered the source, on March 28, when it erupted with the first in a series of X-ray blasts.

Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by University of Warwick.

Journal Reference:

A. J. Levan, N. R. Tanvir, S. B. Cenko, D. A. Perley, K. Wiersema, J. S. Bloom, A. S. Fruchter, A. De Ugarte Postigo, P. T. O’brien, N. Butler, A. J. Van Der Horst, G. Leloudas, A. N. Morgan, K. Misra, G. C. Bower, J. Farihi, R. L. Tunnicliffe, M. Modjaz, J. M. Silverman, J. Hjorth, C. Thöne, A. Cucchiara, J. M. Castro Cerón, A. J. Castro-Tirado, J. A. Arnold, M. Bremer, J. P. Brodie, T. Carroll, M. C. Cooper, P. A. Curran, R. M. Cutri, J. Ehle, D. Forbes, J. Fynbo, J. Gorosabel, J. Graham, D. I. Hoffman, S. Guziy, P. Jakobsson, A. Kamble, T. Kerr, M. M. Kasliwal, C. Kouveliotou, D. Kocesvki, N. M. Law, P. E. Nugent, E. O. Ofek, D. Poznanski, R. M. Quimby, E. Rol, A. J. Romanowsky, R. Sánchez-Ramírez, S. Schulze, N. Singh, L. Van Spaandonk, R. L. C. Starling, R. G. Strom, J. C. Tello, O. Vaduvescu, P. J. Wheatley, R. A. M. J. Wijers, J. M. Winters, and D. Xu. An Extremely Luminous Panchromatic Outburst from the Nucleus of a Distant Galaxy. Science, 16 June 2011 DOI: 10.1126/science.1207143

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Nearby galaxy boasts two monster black holes, both active

ScienceDaily (June 11, 2011) — A study using NASA's Swift satellite and the Chandra X-ray Observatory has found a second supersized black hole at the heart of an unusual nearby galaxy already known to be sporting one.

The galaxy, which is known as Markarian 739 or NGC 3758, lies 425 million light-years away toward the constellation Leo. Only about 11,000 light-years separate the two cores, each of which contains a black hole gorging on infalling gas.

The study will appear in a forthcoming issue of The Astrophysical Journal Letters.

"At the hearts of most large galaxies, including our own Milky Way, lies a supermassive black hole weighing millions of times the sun's mass," said Michael Koss, the study's lead author at NASA's Goddard Space Flight Center in Greenbelt, Md., and the University of Maryland in College Park (UMCP). "Some of them radiate billions of times as much energy as the sun."

Astronomers refer to galaxy centers exhibiting such intense emission as active galactic nuclei (AGN). Yet as common as monster black holes are, only about one percent of them are currently powerful AGN. Binary AGN are rarer still: Markarian 739 is only the second identified within half a billion light-years.

Many scientists think that disruptive events like galaxy collisions trigger AGN to switch on by sending large amounts of gas toward the black hole. As the gas spirals inward, it becomes extremely hot and radiates huge amounts of energy.

Since 2004, the Burst Alert Telescope (BAT) aboard Swift has been mapping high-energy X-ray sources all around the sky. The survey is sensitive to AGN up to 650 million light-years away and has uncovered dozens of previously unrecognized systems. Follow-up studies by Koss and colleagues published in 2010 reveal that about a quarter of the Swift BAT AGN were either interacting or in close pairs, with perhaps 60 percent of them poised to merge in another billion years.

"If two galaxies collide and each possesses a supermassive black hole, there should be times when both black holes switch on as AGN," said coauthor Richard Mushotzky, professor of astronomy at UMCP. "We weren't seeing many double AGN, so we turned to Chandra for help."

Swift's BAT instrument is scanning one-tenth of the sky at any given moment, its X-ray survey growing more sensitive every year as its exposure increases. Where Swift's BAT provided a wide-angle view, the X-ray telescope aboard the Chandra X-ray Observatory acted like a zoom lens and resolved details a hundred times smaller.

For decades, astronomers have known that the eastern nucleus of Markarian 739 contains a black hole that is actively accreting matter and generating prodigious energy. The Chandra study shows that its western neighbor is too. This makes the galaxy one of the nearest and clearest cases of a binary AGN.

The distance separating the two black holes is about a third of the distance separating the solar system from the center of our own galaxy. The dual AGN of Markarian 739 is the second-closest known, both in terms of distance from one another and distance from Earth. However, another galaxy known as NGC 6240 holds both records.

How did the second AGN remain hidden for so long? "Markarian 739 West shows no evidence of being an AGN in visible, ultraviolet and radio observations," said coauthor Sylvain Veilleux, a professor of astronomy at UMCP. "This highlights the critical importance of high-resolution observations at high X-ray energies in locating binary AGN."

The research team also includes Ezequiel Treister and David Sanders at the University of Hawaii's Institute for Astronomy in Honolulu, Kevin Schawinski at Yale University in New Haven, Conn., and Ranjan Vasudevan, Neal Miller and Margaret Trippe at the University of Maryland, College Park.

Swift, launched in November 2004, is managed by Goddard. It was built and is being operated in collaboration with Penn State University, 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.

The Marshall Space Flight Center manages the Chandra program for NASA's Science Mission Directorate in Washington. The Smithsonian Astrophysical Observatory controls Chandra's science and flight operations from Cambridge, Mass.

For more information, images and video, please visit: http://www.nasa.gov/mission_pages/swift/bursts/monster-black-holes.html

Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by NASA/Goddard Space Flight Center.

Note: If no author is given, the source is cited instead.

Disclaimer: Views expressed in this article do not necessarily reflect those of ScienceDaily or its staff.

View the original article here

Nearby galaxy boasts two monster black holes, both active

ScienceDaily (June 11, 2011) — A study using NASA's Swift satellite and the Chandra X-ray Observatory has found a second supersized black hole at the heart of an unusual nearby galaxy already known to be sporting one.

The galaxy, which is known as Markarian 739 or NGC 3758, lies 425 million light-years away toward the constellation Leo. Only about 11,000 light-years separate the two cores, each of which contains a black hole gorging on infalling gas.

The study will appear in a forthcoming issue of The Astrophysical Journal Letters.

"At the hearts of most large galaxies, including our own Milky Way, lies a supermassive black hole weighing millions of times the sun's mass," said Michael Koss, the study's lead author at NASA's Goddard Space Flight Center in Greenbelt, Md., and the University of Maryland in College Park (UMCP). "Some of them radiate billions of times as much energy as the sun."

Astronomers refer to galaxy centers exhibiting such intense emission as active galactic nuclei (AGN). Yet as common as monster black holes are, only about one percent of them are currently powerful AGN. Binary AGN are rarer still: Markarian 739 is only the second identified within half a billion light-years.

Many scientists think that disruptive events like galaxy collisions trigger AGN to switch on by sending large amounts of gas toward the black hole. As the gas spirals inward, it becomes extremely hot and radiates huge amounts of energy.

Since 2004, the Burst Alert Telescope (BAT) aboard Swift has been mapping high-energy X-ray sources all around the sky. The survey is sensitive to AGN up to 650 million light-years away and has uncovered dozens of previously unrecognized systems. Follow-up studies by Koss and colleagues published in 2010 reveal that about a quarter of the Swift BAT AGN were either interacting or in close pairs, with perhaps 60 percent of them poised to merge in another billion years.

"If two galaxies collide and each possesses a supermassive black hole, there should be times when both black holes switch on as AGN," said coauthor Richard Mushotzky, professor of astronomy at UMCP. "We weren't seeing many double AGN, so we turned to Chandra for help."

Swift's BAT instrument is scanning one-tenth of the sky at any given moment, its X-ray survey growing more sensitive every year as its exposure increases. Where Swift's BAT provided a wide-angle view, the X-ray telescope aboard the Chandra X-ray Observatory acted like a zoom lens and resolved details a hundred times smaller.

For decades, astronomers have known that the eastern nucleus of Markarian 739 contains a black hole that is actively accreting matter and generating prodigious energy. The Chandra study shows that its western neighbor is too. This makes the galaxy one of the nearest and clearest cases of a binary AGN.

The distance separating the two black holes is about a third of the distance separating the solar system from the center of our own galaxy. The dual AGN of Markarian 739 is the second-closest known, both in terms of distance from one another and distance from Earth. However, another galaxy known as NGC 6240 holds both records.

How did the second AGN remain hidden for so long? "Markarian 739 West shows no evidence of being an AGN in visible, ultraviolet and radio observations," said coauthor Sylvain Veilleux, a professor of astronomy at UMCP. "This highlights the critical importance of high-resolution observations at high X-ray energies in locating binary AGN."

The research team also includes Ezequiel Treister and David Sanders at the University of Hawaii's Institute for Astronomy in Honolulu, Kevin Schawinski at Yale University in New Haven, Conn., and Ranjan Vasudevan, Neal Miller and Margaret Trippe at the University of Maryland, College Park.

Swift, launched in November 2004, is managed by Goddard. It was built and is being operated in collaboration with Penn State University, 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.

The Marshall Space Flight Center manages the Chandra program for NASA's Science Mission Directorate in Washington. The Smithsonian Astrophysical Observatory controls Chandra's science and flight operations from Cambridge, Mass.

For more information, images and video, please visit: http://www.nasa.gov/mission_pages/swift/bursts/monster-black-holes.html

Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by NASA/Goddard Space Flight Center.

Note: If no author is given, the source is cited instead.

Disclaimer: Views expressed in this article do not necessarily reflect those of ScienceDaily or its staff.

View the original article here

NASA's Chandra finds massive black holes common in early universe

ScienceDaily (June 15, 2011) — Using the deepest X-ray image ever taken, astronomers found the first direct evidence that massive black holes were common in the early universe. This discovery from NASA's Chandra X-ray Observatory shows that very young black holes grew more aggressively than previously thought, in tandem with the growth of their host galaxies.

By pointing Chandra at a patch of sky for more than six weeks, astronomers obtained what is known as the Chandra Deep Field South (CDFS). When combined with very deep optical and infrared images from NASA's Hubble Space Telescope, the new Chandra data allowed astronomers to search for black holes in 200 distant galaxies, from when the universe was between about 800 million to 950 million years old.

"Until now, we had no idea what the black holes in these early galaxies were doing, or if they even existed," said Ezequiel Treister of the University of Hawaii, lead author of the study appearing in the June 16 issue of the journal Nature. "Now we know they are there, and they are growing like gangbusters."

The super-sized growth means that the black holes in the CDFS are less extreme versions of quasars -- very luminous, rare objects powered by material falling onto supermassive black holes. However, the sources in the CDFS are about a hundred times fainter and the black holes are about a thousand times less massive than the ones in quasars.

The observations found that between 30 and 100 percent of the distant galaxies contain growing supermassive black holes. Extrapolating these results from the small observed field to the full sky, there are at least 30 million supermassive black holes in the early universe. This is a factor of 10,000 larger than the estimated number of quasars in the early universe.

"It appears we've found a whole new population of baby black holes," said co-author Kevin Schawinski of Yale University. "We think these babies will grow by a factor of about a hundred or a thousand, eventually becoming like the giant black holes we see today almost 13 billion years later."

A population of young black holes in the early universe had been predicted, but not yet observed. Detailed calculations show that the total amount of black hole growth observed by this team is about a hundred times higher than recent estimates.

Because these black holes are nearly all enshrouded in thick clouds of gas and dust, optical telescopes frequently cannot detect them. However, the high energies of X-ray light can penetrate these veils, allowing the black holes inside to be studied.

Physicists studying black holes want to know more how the first supermassive black holes were formed and how they grow. Although evidence for parallel growth of black holes and galaxies has been established at closer distances, the new Chandra results show that this connection starts earlier than previously thought, perhaps right from the origin of both.

"Most astronomers think in the present-day universe, black holes and galaxies are somehow symbiotic in how they grow," said Priya Natarajan, a co-author from Yale University. "We have shown that this codependent relationship has existed from very early times."

It has been suggested that early black holes would play an important role in clearing away the cosmic "fog" of neutral, or uncharged, hydrogen that pervaded the early universe when temperatures cooled down after the Big Bang. However, the Chandra study shows that blankets of dust and gas stop ultraviolet radiation generated by the black holes from traveling outwards to perform this "reionization." Therefore, stars and not growing black holes are likely to have cleared this fog at cosmic dawn.

Chandra is capable of detecting extremely faint objects at vast distances, but these black holes are so obscured that relatively few photons can escape and hence they could not be individually detected. Instead, the team used a technique that relied on Chandra's ability to accurately determine the direction from which the X-rays came to add up all the X-ray counts near the positions of distant galaxies and find a statistically significant signal.

NASA's Marshall Space Flight Center in Huntsville, Ala., manages the Chandra program for the agency's Science Mission Directorate in Washington. The Smithsonian Astrophysical Observatory controls Chandra's science and flight operations from Cambridge, Mass.

More information, including images and other multimedia, can be found at: http://chandra.si.edu

Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by NASA.

Journal Reference:

Ezequiel Treister, Kevin Schawinski, Marta Volonteri, Priyamvada Natarajan, Eric Gawiser. Black hole growth in the early Universe is self-regulated and largely hidden from view. Nature, 2011; 474 (7351): 356 DOI: 10.1038/nature10103

Note: If no author is given, the source is cited instead.

Disclaimer: Views expressed in this article do not necessarily reflect those of ScienceDaily or its staff.

View the original article here

Black hole kills star and blasts 3.8 billion light year beam at Earth

ScienceDaily (June 16, 2011) — Research led by astronomers at the University of Warwick has confirmed that the flash from one of the biggest and brightest bangs yet recorded by astronomers comes from a massive black hole at the centre of a distant galaxy. The black hole appears to have ripped apart a star that wandered too close, creating a powerful beam of energy that crossed the 3.8 billion light years to Earth.

Their research was published June 16 in the Journal Science.

The high energy X-rays and gamma-rays persisted at an extremely bright level for weeks after the event, with bright flares arising when further chunks of the star fell into the black hole. The extreme brightness of this event comes from the fact that it illuminated only a small fraction of the sky, pointing a jet of light towards the Milky Way, which was detected at Earth 3.8 billion years after the star was ripped apart.

Dr Andrew Levan, lead researcher on the paper from the University of Warwick, said: "Despite the power of this the cataclysmic event we still only happen to see this event because our solar system happened to be looking right down the barrel of this jet of energy."

The new research paper clearly establishes that the source of this event -- known now as Sw 1644+57 -- is right at the heart of far away galaxy, 3.8 billion light years away, at a spot which would be in the constellation Draco.

University of Warwick researcher Dr Andrew Levan said: "The only explanation that so far fits the size, intensity, time scale, and level of fluctuation of the observed event, is that a massive black at the very centre of that galaxy has pulled in a large star and ripped it apart by tidal disruption. The spinning black hole then created the two jets one of which pointed straight to earth."

The researchers used the Hubble Space Telescope, Swift satellite and the Chandra X-ray Observatory to study the blast. Swift's Burst Alert Telescope first discovered the source, on March 28, when it erupted with the first in a series of X-ray blasts.

Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by University of Warwick.

Journal Reference:

A. J. Levan, N. R. Tanvir, S. B. Cenko, D. A. Perley, K. Wiersema, J. S. Bloom, A. S. Fruchter, A. De Ugarte Postigo, P. T. O’brien, N. Butler, A. J. Van Der Horst, G. Leloudas, A. N. Morgan, K. Misra, G. C. Bower, J. Farihi, R. L. Tunnicliffe, M. Modjaz, J. M. Silverman, J. Hjorth, C. Thöne, A. Cucchiara, J. M. Castro Cerón, A. J. Castro-Tirado, J. A. Arnold, M. Bremer, J. P. Brodie, T. Carroll, M. C. Cooper, P. A. Curran, R. M. Cutri, J. Ehle, D. Forbes, J. Fynbo, J. Gorosabel, J. Graham, D. I. Hoffman, S. Guziy, P. Jakobsson, A. Kamble, T. Kerr, M. M. Kasliwal, C. Kouveliotou, D. Kocesvki, N. M. Law, P. E. Nugent, E. O. Ofek, D. Poznanski, R. M. Quimby, E. Rol, A. J. Romanowsky, R. Sánchez-Ramírez, S. Schulze, N. Singh, L. Van Spaandonk, R. L. C. Starling, R. G. Strom, J. C. Tello, O. Vaduvescu, P. J. Wheatley, R. A. M. J. Wijers, J. M. Winters, and D. Xu. An Extremely Luminous Panchromatic Outburst from the Nucleus of a Distant Galaxy. Science, 16 June 2011 DOI: 10.1126/science.1207143

Note: If no author is given, the source is cited instead.

Disclaimer: Views expressed in this article do not necessarily reflect those of ScienceDaily or its staff.

View the original article here

Gamma-ray flash came from star being eaten by massive black hole

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NASA's Chandra finds massive black holes common in early universe

ScienceDaily (June 15, 2011) — Using the deepest X-ray image ever taken, astronomers found the first direct evidence that massive black holes were common in the early universe. This discovery from NASA's Chandra X-ray Observatory shows that very young black holes grew more aggressively than previously thought, in tandem with the growth of their host galaxies.

By pointing Chandra at a patch of sky for more than six weeks, astronomers obtained what is known as the Chandra Deep Field South (CDFS). When combined with very deep optical and infrared images from NASA's Hubble Space Telescope, the new Chandra data allowed astronomers to search for black holes in 200 distant galaxies, from when the universe was between about 800 million to 950 million years old.

"Until now, we had no idea what the black holes in these early galaxies were doing, or if they even existed," said Ezequiel Treister of the University of Hawaii, lead author of the study appearing in the June 16 issue of the journal Nature. "Now we know they are there, and they are growing like gangbusters."

The super-sized growth means that the black holes in the CDFS are less extreme versions of quasars -- very luminous, rare objects powered by material falling onto supermassive black holes. However, the sources in the CDFS are about a hundred times fainter and the black holes are about a thousand times less massive than the ones in quasars.

The observations found that between 30 and 100 percent of the distant galaxies contain growing supermassive black holes. Extrapolating these results from the small observed field to the full sky, there are at least 30 million supermassive black holes in the early universe. This is a factor of 10,000 larger than the estimated number of quasars in the early universe.

"It appears we've found a whole new population of baby black holes," said co-author Kevin Schawinski of Yale University. "We think these babies will grow by a factor of about a hundred or a thousand, eventually becoming like the giant black holes we see today almost 13 billion years later."

A population of young black holes in the early universe had been predicted, but not yet observed. Detailed calculations show that the total amount of black hole growth observed by this team is about a hundred times higher than recent estimates.

Because these black holes are nearly all enshrouded in thick clouds of gas and dust, optical telescopes frequently cannot detect them. However, the high energies of X-ray light can penetrate these veils, allowing the black holes inside to be studied.

Physicists studying black holes want to know more how the first supermassive black holes were formed and how they grow. Although evidence for parallel growth of black holes and galaxies has been established at closer distances, the new Chandra results show that this connection starts earlier than previously thought, perhaps right from the origin of both.

"Most astronomers think in the present-day universe, black holes and galaxies are somehow symbiotic in how they grow," said Priya Natarajan, a co-author from Yale University. "We have shown that this codependent relationship has existed from very early times."

It has been suggested that early black holes would play an important role in clearing away the cosmic "fog" of neutral, or uncharged, hydrogen that pervaded the early universe when temperatures cooled down after the Big Bang. However, the Chandra study shows that blankets of dust and gas stop ultraviolet radiation generated by the black holes from traveling outwards to perform this "reionization." Therefore, stars and not growing black holes are likely to have cleared this fog at cosmic dawn.

Chandra is capable of detecting extremely faint objects at vast distances, but these black holes are so obscured that relatively few photons can escape and hence they could not be individually detected. Instead, the team used a technique that relied on Chandra's ability to accurately determine the direction from which the X-rays came to add up all the X-ray counts near the positions of distant galaxies and find a statistically significant signal.

NASA's Marshall Space Flight Center in Huntsville, Ala., manages the Chandra program for the agency's Science Mission Directorate in Washington. The Smithsonian Astrophysical Observatory controls Chandra's science and flight operations from Cambridge, Mass.

More information, including images and other multimedia, can be found at: http://chandra.si.edu

Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by NASA.

Journal Reference:

Ezequiel Treister, Kevin Schawinski, Marta Volonteri, Priyamvada Natarajan, Eric Gawiser. Black hole growth in the early Universe is self-regulated and largely hidden from view. Nature, 2011; 474 (7351): 356 DOI: 10.1038/nature10103

Note: If no author is given, the source is cited instead.

Disclaimer: Views expressed in this article do not necessarily reflect those of ScienceDaily or its staff.

View the original article here

Astrophysicists use X-ray fingerprints to study eating habits of giant black holes

ScienceDaily (June 7, 2011) — By studying the X-rays emitted when superheated gases plunge into distant and massive black holes, astrophysicists at the Georgia Institute of Technology have provided an important test of a long-standing theory that describes the extreme physics occurring when matter spirals into these massive objects.

Matter falling into black holes emits tremendous amounts of energy which can escape as visible light, ultraviolet light and X-rays. This energy can also drive outflows of gas and dust far from the black hole, affecting the growth and evolution of galaxies containing the black holes. Understanding the complex processes that occur in these active galactic nuclei is vital to theories describing the formation of galaxies such as the Milky Way, and is therefore the subject of intense research.

Though light cannot escape from black holes themselves, black holes with accretion disks -- which are swirling clouds of matter about to enter the black hole -- are among the most luminous objects in galaxies. By studying how the radiation and accretion disk interact, astrophysicists can learn much about the extreme gravitational fields, magnetic forces and radiation processes close to these black holes.

"We reviewed data collected from space telescopes over the past few years and found that the more rapidly a black hole was gobbling up material, the more highly ionized the accretion disk was," said David Ballantyne, an assistant professor in Georgia Tech's School of Physics. "The simple theory of accretion disks predicts this, but the relationship we saw between the ionization and rate of accretion was different from what the theory predicted."

The large difference between the observed and theoretical relationships -- a linear dependence on the rate of accretion as opposed to a cubic dependence -- is not surprising for a phenomenon that can't exactly be tested under controlled laboratory conditions. In a paper published online June 3 in The Astrophysical Journal, Ballantyne describes the research and speculates about possible reasons for the difference between observations and theory. The research, which will appear in the Journal's June 20 issue, was supported in part by the National Science Foundation (NSF).

"As in many areas of science, especially astronomy, we end up needing more data -- many more high-quality observations to better define this relationship," he added.

Astrophysicists don't have a detailed understanding of how the accretion process works, why black holes grow at different rates -- or what makes them stop growing. These questions are important because the growth of active galactic nuclei -- the black holes and their surrounding accretion disks -- has broader effects on the galaxies of which they are part.

"The rapid accretion phase releases a lot of energy, not only in radiation, but also in outflows that drive gas out of a galaxy, which can shut off star formation and hold back the growth of the galaxy," said Ballantyne, a scientist in Georgia Tech's Center for Relativistic Astrophysics. "We could potentially learn something fundamental about the flow of energy through the accretion disk very close to the black hole. We could learn about the viscosity of this matter and how efficiently radiation transport takes place. These are very important questions in astrophysics."

X-rays are believed to originate from innermost portion of active galactic nuclei. As they pass through matter on its way into the black hole, the X-rays are altered by the materials in ways that astrophysicists can measure. In their study, Ballantyne and his collaborators were interested in studying the ionization state of the matter -- which is related to the illumination -- and were able to do so by analyzing the "fingerprint" the ionization left on the X-rays.

"From laboratory work, we understand the physics of how gas interacts with X-ray radiation because that's basically an atomic physics problem," he explained. "We can model what these fingerprints might look like on the X-rays, and compare that to the actual data to help us understand what's going on."

Because of their high energy and short wavelength, X-rays pass through many materials, such as human bodies, with little attenuation. This makes them ideal for examining processes in active galactic nuclei. Longer wavelengths, such as ultraviolet and visible light, are absorbed by intergalactic dust, or are difficult to distinguish from light originating in stars. However, X-rays do get absorbed by dense objects, such as bones -- and crucially for this study -- accretion disks.

Ballantyne and his collaborators Jon McDuffie and John Rusin studied ten X-ray observations reported by other scientists from eight different active galactic nuclei. The observations were made using such space telescopes as Chandra and XMM.

To be useful, they used only measurements of X-ray emissions from the innermost and hottest portion of the accretion disk, and only where the mass of the black holes -- which range from a million to a billion times the size of our sun -- had high quality estimates.

In pursuing the study, Ballantyne hopes to maintain the involvement of Rusin, a student from South Cobb High School in Marietta, near Atlanta. Rusin became involved when he contacted Georgia Tech to inquire about astrophysics projects.

"He helped us with data acquisition and was a really big help," said Ballantyne. "I treated him just like an undergraduate student. I'm pleased to know that he has decided to attend Georgia Tech."

The next step in the research will be to gather additional information from other studies of active galactic nuclei to see if the linear relationship Ballantyne's group measured holds up. The work may also lead to other techniques for learning about black holes and the accretion process.

"Black holes themselves are very simple, but what goes on around them can be very complex," Ballantyne said. "There is still a lot to be learned about how black holes get fueled, and how some accrete slowly while others grow rapidly. The astrophysics of black holes is actually very important in determining what our universe looks like."

Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by Georgia Institute of Technology Research News. The original article was written by John Toon.

Journal Reference:

D. R. Ballantyne, J. R. McDuffie, J. S. Rusin. A Correlation between the Ionization State of the Inner Accretion Disk and the Eddington Ratio of Active Galactic Nuclei. The Astrophysical Journal, 2011; 734 (2): 112 DOI: 10.1088/0004-637X/734/2/112

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Disclaimer: Views expressed in this article do not necessarily reflect those of ScienceDaily or its staff.

View the original article here