* Astronomy

Members Login
Post Info TOPIC: blackhole spectra


L

Posts: 131433
Date:
X-ray survey finds dozens of giant, ravenous black holes
Permalink  
 


About 160 supermassive black holes have been found feasting on matter at the centres of nearby galaxies, reveals an X-ray survey of the entire sky by NASA's Swift satellite.

More than 300 X-ray sources were found in the survey. Some were galaxy clusters and some have yet to be identified, while 158 were identified as active galactic nuclei (AGN). These are strongly radiating objects at the centres of galaxies that are thought to be black holes as massive as millions or billions of times the Sun that are devouring nearby matter.
Many of the black holes would not have been found with surveys probing visible light or other wavelengths, which cannot pass through the thick dust surrounding many of them. So Swift's X-ray survey, which is ongoing, provides a complete census of relatively nearby AGNs.

click here to read more.

__________________


L

Posts: 131433
Date:
The Nature Of Black Hole Jets
Permalink  
 


NASA and Italian scientists using Swift have for the first time determined what the particle jets streaming from black holes are made of.

Black hole particle jets are commonly seen in quasars and other celestial objects, shooting off at nearly light speed. According to the Swift team, these jets appear to be made of protons and electrons, solving a mystery as old as the discovery of jets themselves in the 1970s. The jets observed by Swift contain about the mass of Jupiter if it were pulverized and blasted out into intergalactic space
Black hole particle jets typically escape the confines of their host galaxies and flow for hundreds of thousands of light years. They are a primary means of redistributing matter and energy in the universe. They are a key to understanding galaxy formation and are tied to numerous cosmic mysteries, such as the origin of ultrahigh-energy cosmic rays.

"Black hole jets are one of the great paradoxes in astronomy. How is it that black holes, so efficient at pulling matter in, can also accelerate matter away at near light speed? We still don't know how these jets form, but at least we now have a solid idea about what they're made of" - Rita Sambruna of NASA's Goddard Space Flight Centre, Greenbelt, Md.

The composition of black hole jets has been the topic of heated debate for several decades. Scientists generally agree that the jets must be made either of electrons and their antimatter partners, called positrons, or an even mix of electrons and protons. Recent theoretical and observational advances have pointed in the direction of the latter. The Swift data provides the most compelling evidence to date that the jets must have protons.
Most quasars have jets. A quasar is bright galaxy core fuelled by a supermassive black hole containing the mass of millions to billions of suns confined within a region about the size of our solar system. The particle jets, usually in opposing pairs, shoot off perpendicularly from the flat disk of gas that swirls around the black hole.
Sambruna's team, comprising researchers at Goddard and the Merate Observatory, Merate, Italy, studied a type of quasar called a blazar. Blazars are quasars with their particle jets aimed in our direction, as if we are staring down the barrel of the gun. The team studied two blazars, called 0212+735 and PKS 0537-286, both over 10 billion light years away.
Previously, telescopes have not been able to capture much detail of black hole jets in a wavelength region between X-rays and gamma rays, corresponding to an energy range of 10 kiloelectron volts (keV) and above. This range, however, is precisely where Swift is most sensitive.
Sambruna's team found a peak in the detection rate of light particles, called photons, at 10 keV and then a downturn. That is, the number of X-ray photons climbed steadily until 10 keV and then declined. From this information and new computer modelling led by Fabrizio Tavecchio and Gabriele Ghisellini at Merate Observatory, the team could rule out the presence of electron-positron pairs.
The analysis took several steps. The Swift data provided enough information to determine the jet was moving at 99.9 percent light speed and contained 200 billion trillion trillion trillion trillion particles. From this, the scientists could determine the total kinetic energy, which is a first. Comparing the kinetic energy of motion with the radiated energy of light, the scientists could determine the mass of the jet and ultimately its content.

"The jet contains about the same mass as Jupiter, which means the central black hole is like a cannon firing a massive pulverized planet at near light speed clear out of the galaxy. That's an enormous amount of energy leaving the black hole system, and this is happening throughout the universe" - Fabrizio Tavecchio.

The finding is a major step towards determining how jets are created, a goal for the Gamma-ray Large Area Space Telescope, or GLAST, planned for launch in autumn 2007.

Source

__________________


L

Posts: 131433
Date:
M87
Permalink  
 


A striking example of the power and effervescence of supermassive black holes is shown in this composite image of the elliptical galaxy M87 in the Virgo Cluster. The features in this image imply that outbursts and deep sounds have been generated by the black hole for eons.

m87SMALL
Expand (452kb, 612 x 612)
Credit NASA
Position(2000): RA 12h 30m 49.50s Dec +12º 23' 28.00

The black hole located in the center of M87 is one of the most massive in the universe. The huge reservoir of hot gas in this cluster is shown in this low energy X-ray image from the Chandra X-ray Observatory (red). An optical image from the Digitized Sky Survey shows stars in M87 in blue.
A series of unevenly spaced loops and bubbles are visible in the hot gas below and to the left of the centre of M87. These features are produced by small outbursts from close to the black hole about once every 6 million years. The sound waves generated by these outbursts, not visible in this image, will be incredibly deep, about 56 octaves below middle C. Because the outbursts are unevenly spaced the sound will be more like noise from the black hole rather than a harmonious musical performance.

See more

__________________


L

Posts: 131433
Date:
SDSSJ084119.52+290504.4
Permalink  
 


Astronomer Tomotsugu Goto from the Japan Aerospace Exploration Agency(JAXA) has used the Subaru telescope to identify a distant quasar powered by a massive black hole. The quasar SDSSJ084119.52+290504.4 is almost 12.7 billion light-years away from Earth in the direction of the constellation Cancer the Crab. It is the most distant one ever found by a Japanese researcher and the eleventh most distant quasar currently known.

The black hole is probably 2 billion times more massive than the Sun. So far, researchers have not yet proposed a theory of how such a massive black hole can form only 1 billion years after the birth of the universe.
Quasars are black holes in the act of actively swallowing material from surrounding space and emitting huge outbursts of energy. They are rare, and astronomers must search over a wide area of sky to find them. To locate candidate quasars, Goto searched the database of the Sloan Digital Sky Survey (SDSS) to find objects that have the same colour in visible light as quasars at a distance of 12.7 billion light years. He found 300 candidates among the 180 million objects scattered in the sky in the 6,670-square-degree area of the SDSS (this covers roughly one-sixth of the sky). By observing these candidates in infrared light using the Apache Point 3.5-meter telescope and the United Kingdom Infrared Telescope on Mauna Kea, Goto was able to eliminate stars in our own galaxy that have similar visible colours to quasars.
Goto then observed the remaining 26 candidates with the Faint Object Camera and Spectrograph (FOCAS) on the Subaru telescope to find what he was looking for a quasar 12.7 billion light years away. Xiaohui Fan from the University of Arizona and his collaborators who discovered the ten most distant quasars known have been the only other researchers successful in finding such distance quasars.
The Goto's newly discovered quasar has a black hole that is probably 2 billion times more massive than the Sun. So far, researchers have no one has not yet proposed a theory of how such a massive black hole could have can formed only a 1 billion years after the birth of the universe.
In addition, the quasar's spectrum shows that much of the hydrogen between the quasar and Earth is ionised. This suggests that something had converted neutral hydrogen to ionised hydrogen before the universe was even a billion years old, something had converted neutral hydrogen to ionised hydrogen, a mysterious event known as the reionisation of the universe.
The most promising solution key to understanding to the riddle of reionisation is ultraviolet radiation. It comes from either stars or massive black holes. However, since reionisation occurred over 12 billion years ago, getting reliable observational evidence has been a challenge.
Quasars are ideal for probing the epoch of reionisation because they are distant and shine brightly and stably over long periods of time. Gamma ray bursts are also extremely distant and bright, and many researchers have used them successfully to probe reionisation. However, as their name implies, gamma-ray bursts only happen occasionally, and do not last a long time.
Quasars are rare, nonetheless, and it takes a search over a wide area of sky to find them. To find candidate quasars, Goto searched the database of the Sloan Digital Sky Survey (SDSS) to find objects that have the same colour in visible light as quasars at a distance of 12.7 billion light years. There were 300 candidates among the 180 million objects scattered in the sky in the 6670 square degree area of the SDSS, covering roughly one sixth of the sky. By observing these candidates in infrared light at the Apache Point 3.5 meter telescope and the United Kingdom Infrared Telescope on Mauna Kea, he was able to eliminate stars in our own galaxy that have similar visible colours to quasars.
Goto then observed the remaining 26 candidates with the Faint Object Camera and Spectrograph (FOCAS) on the Subaru telescope to find what he was looking for - a quasar 12.7 billion light years away. Xiaohui Fan from the University of Arizona and his collaborators who discovered the ten most distant quasars known have been the only other researchers successful in finding such distance quasars.

Reionisation of the universe is a patchy affair, progressing faster in regions with more ionising sources. To truly understand how this process occurs, its process, it is important to find probes of reionisation in as many directions as possible and at a range of distances. Goto hopes to repeat his success with even more distant quasars

This research will be published in the Monthly Notices of the Royal Astronomical Society.

Source

__________________


L

Posts: 131433
Date:
MECO
Permalink  
 



A controversial alternative to black hole theory has been bolstered by observations of an object in the distant universe, researchers say. If their interpretation is correct, it might mean black holes do not exist and are in fact bizarre and compact balls of plasma called MECOs.

Rudolph Schild of the Harvard-Smithsonian Centre for Astrophysics in Cambridge, Massachusetts, US, led a team that observed a quasar situated 9 billion light years from Earth. A quasar is a very bright, compact object, whose radiation is usually thought to be generated by a giant black hole devouring its surrounding matter.
A rare cosmological coincidence allowed Schild and his colleagues to probe the structure of the quasar in much finer detail than is normally possible. Those details suggest that the central object is not a black hole.

"The structure of the quasar is not at all what had been theorised" - Rudolph Schild.

A black hole, as traditionally understood, is an object with such a powerful gravitational field that even light is not fast enough to escape it. Anything that gets within a certain distance of the black hole's centre, called the event horizon, will be trapped.
A well accepted property of black holes is that they cannot sustain a magnetic field of their own. But observations of quasar Q0957+561 indicate that the object powering it does have a magnetic field. For this reason, they believe that rather than a black hole, this quasar contains something called a magnetospheric eternally collapsing object (MECO). If so, it would be best evidence yet for such an object.

The researchers used gravitational lensing to make their close observation of the quasar. This technique exploits rare coincidences that can occur when a galaxy sits directly between a distant object and observers on Earth.
The gravity of the intervening galaxy acts like a lens. As the intervening galaxy's individual stars pass in front of the quasar, this bending varies, making the quasar appear to flicker.
Carefully scrutinising this flickering allowed the researchers to probe fine details of the quasar's structure that are normally far too small to be resolved by even the most powerful telescopes.
Magnetic sweep
The researchers found that the disc of material surrounding the central object has a hole in it with a width of about 4000 Astronomical Units (1 AU is the distance between the Earth and the Sun). This gap suggests that material has been swept out by magnetic forces from the central object, the researchers say, and must therefore be a MECO, not a black hole.

"I believe this is the first evidence that the whole black hole paradigm is incorrect" - Darryl Leiter of the Marwood Astrophysics Research Center in Charottesville, Virginia, US, who co-authored the study.

He says that where astronomers think they see black holes, they are actually looking at MECOs.
According to the MECO theory, objects in our universe can never actually collapse to form black holes. When an object gets very dense and hot, subatomic particles start popping in and out of existence inside it in huge numbers, producing copious amounts of radiation. Outward pressure from this radiation halts the collapse so the object remains a hot ball of plasma rather than becoming a black hole.
Extremely complex
But Chris Reynolds of the University of Maryland, in Baltimore, US, says the evidence for a MECO inside this quasar is not convincing. The apparent hole in the disc could be filled with very hot, tenuous gas, which would not radiate much and would be hard to see.

"Especially if you're looking with an optical telescope, which is how these observations were made, you wouldn't see that gas at all" - Chris Reynolds.

Leiter says this scenario would leave other things unexplained, however. The observations show that a small ring at the inner edge of the disc is glowing, which is a sign that it has been heated by a strong magnetic field, he says. In Reynolds's scenario, one would expect a much broader section of the disc to be heated.

In any case, says Reynolds, it is difficult to draw conclusions from the team's detailed comparisons of their observations with models of black holes because those models are far from definitive.

"We know the accretion of gas into black holes is an extremely complex phenomenon. We don’t know precisely what that would look like. It would be truly exciting if there was compelling evidence found for a non-black-hole object in these quasars. I just don't think that this fits." - Chris Reynolds.

__________________


L

Posts: 131433
Date:
GRO J1655-40
Permalink  
 


GRO J1655-40: NASA's Chandra Answers Black Hole Paradox

The temperature and intensity of the winds imply that powerful magnetic fields must be present. These magnetic fields, likely carried by the gas flowing from the companion star, create magnetic turbulence that generates friction in the gaseous disk and drive winds from the disk that carry momentum outward as the gas falls inward. Magnetic friction also heats the gas in the inner part of the disk to X-ray emitting temperatures.
The analysis of the disk wind of GRO J1655-40, or J1655 for short, confirmed what astronomers had long suspected, namely that magnetic friction is central to understanding how black holes accrete matter rapidly. Without a process to take away some of the angular momentum of the gas, it could remain in orbit around a black hole for a very long time.


Expand (322.4 kb, 972 x 720)
Credit NASA
Position (2000): RA 16h 54m 00.14s | Dec -39º 50' 44.90"

J1655 is a binary system that harbours a black hole with a mass seven times that of the sun, which is pulling matter from a normal star about twice as massive as the sun.
The Chandra observation revealed a bright X-ray source whose spectrum showed dips produced by absorption from a wide variety of atoms ranging from oxygen to nickel. A detailed study of these absorption features shows that the atoms are highly ionised and are moving away from the black hole in a high-speed wind.
Understanding the importance of magnetic forces in the disk of gas around J1655 could have far-reaching implications, from the supermassive black holes associated with powerful quasars, to planet-forming disks around young sun-like stars.

Source

__________________


L

Posts: 131433
Date:
GROJ1655-40
Permalink  
 


Title: On the distance of GRO J1655-40
Authors: C. Foellmi (ESO+LAOG, France), E. Depagne (ESO+U.Catolica, Chile), T. H. Dall (ESO), I. F. Mirabel (ESO)

Researchers challenge the accepted distance of 3.2 kpc of GRO J1655-40. They present VLT-UVES spectroscopic observations to estimate the absorption toward the source, and determine a maximum distance of GRO J1655-40. They show that the accepted value of 3.2 kpc is taken for granted by many authors. The researchers retrieved in the ESO archive UVES spectra taken in April 2004 when GRO J1655-40 was in quiescence to determine the spectral type of the secondary star. For the first time they build a flux-calibrated mean (UVES) spectrum of GRO J1655-40 and compare its observed flux to that of five nearby stars of similar spectral types.
They strengthen their results with the traditional pair method, using published photometric data of the comparison stars. They show that the distance of 3.2 kpc is questionable, and determine a spectral type F6IV for the secondary star. They also demonstrate in details that the distance of GRO J1655-40 must be smaller than 1.7 kpc.
The runaway black hole GRO J1655-40 could be associated with the open cluster NGC 6242 which is located at 1.0 ±0.1 kpc from the Sun. At D s 1.7 kpc the jets are not a superluminal, and GRO J1655-40 becomes one of the closest known black holes to the Sun.

Read more (694kb, PDF)

__________________


L

Posts: 131433
Date:
Blackholes
Permalink  
 


A University of Mississippi physicist thinks soap bubbles can help scientists better understand the properties of black holes.

Vitor Cardoso, a postdoctoral research associate in the UM Department of Physics and Astronomy, specialises in studies of black holes, mysterious objects in space that have intrigued astronomers and science fiction writers alike for decades. He and Oscar Dias, a postdoctoral fellow at the Perimeter Institute in Canada, collaborate on new projects examining the objects.

"Evidence for a membrane-like behaviour of black holes has been known for two decades, in work pioneered by Kip Thorne and his colleagues. This membrane paradigm approach makes calculations easier" - Vitor Cardoso

Cardoso and Dias have extended and strengthened this analogy. Their combined efforts show that by endowing the membrane with surface tension – the force that holds soap bubbles together – one can reproduce many phenomena, which up to now could be studied only through series of complex computations.
The duo has been applying the membrane paradigm to their study of “black strings,” which are long and thin black holes. The researchers showed these black strings break into smaller fragments, just as water dripping from a faucet breaks into small droplets.

"[I] What's most amazing to me in our results is how such a complex system of equations such as Einstein’s can be modelled so well by fluids with surface tension, like soap bubbles. I was stunned when I saw how good the match was" - Oscar Dias.

Cardoso and Dias recently had an article on their theory accepted for publication in Physical Review Letters, journal of the American Physical Society. The paper, “Gregory-Laflamme and Rayleigh-Plateau Instabilities of Black Strings,” runs in the May 12 issue.

In space, black holes are created when very large stars burn most of their hydrogen and collapse, developing a gravitational power so strong that even light can’t escape their grip. Even more massive ones are seen at the centre of most galaxies.
While the very dense “hole” is pulling more matter into it, devouring it and becoming ever-larger, scientists also believe it is evaporating at the same time.

"Soap bubbles seem to be a good tool to understand black holes. Many important features of black holes may help us understand more deeply the physics behind Einstein’s theory" - Vitor Cardoso.

Source: University of Mississippi

__________________


L

Posts: 131433
Date:
Black Hole Limits
Permalink  
 


The Chandra X-ray telescope confirms Black Hole limits

The very largest black holes reach a certain point and then grow no more, according to the best survey to date of black holes made with the Chandra X-ray Observatory. Scientists have also discovered many previously hidden black holes that are well below their weight limit.
These new results corroborate recent theoretical work about how black holes and galaxies grow. The biggest black holes, those with at least 100 million times the mass of the Sun, ate voraciously during the early Universe. Nearly all of them ran out of 'food' billions of years ago and went onto a forced starvation diet.
On the other hand, black holes between about 10 and 100 million solar masses followed a more controlled eating plan. Because they took smaller portions of their meals of gas and dust, they continue growing today.

"Our data show that some supermassive black holes seem to binge, while others prefer to graze. We now understand better than ever before how supermassive black holes grow" - Amy Barger, University of Wisconsin in Madison and the University of Hawaii, lead author of the paper describing the results in the latest issue of The Astronomical Journal (Feb 2005).

One revelation is that there is a strong connection between the growth of black holes and the birth of stars. Previously, astronomers had done careful studies of the birth-rate of stars in galaxies, but didn't know as much about the black holes at their centres.

"These galaxies lose material into their central black holes at the same time that they make their stars. So whatever mechanism governs star formation in galaxies also governs black hole growth" - Amy Barger

Astronomers have made an accurate census of both the biggest, active black holes in the distance, and the relatively smaller, calmer ones closer by. Now, for the first time, the ones in between have been counted properly.

"We need to have an accurate head count over time of all growing black holes if we ever hope to understand their habits, so to speak" - co-author Richard Mushotzky, NASA's Goddard Space Flight Centre.

Supermassive black holes themselves are invisible, but heated gas around them -- some of which will eventually fall into the black hole - produces copious amounts of radiation in the centres of galaxies as the black holes grow.
This study relied on the deepest X-ray images ever obtained, the Chandra Deep Fields North and South, plus a key wider-area survey of an area called the "Lockman Hole" in the constellation Ursa Major.
The distances to the X-ray sources were determined by optical spectroscopic follow-up at the Keck 10-meter telescope on Mauna Kea in Hawaii, and show the black holes range from less than a billion to 12 billion light years away.
Since X-rays can penetrate the gas and dust that block optical and ultraviolet emission, the very long-exposure X-ray images are crucial to find black holes that otherwise would go unnoticed.


Lockman Hole
Position (2000) : RA = 10h 34m 00.00 Dec = +57° 40' 00.00

Chandra found that many of the black holes smaller than about 100 million Suns are buried under large amounts of dust and gas, which prevents detection of the optical light from the heated material near the black hole. The X-rays are more energetic and are able to burrow through this dust and gas. However, the largest of the black holes show little sign of obscuration by dust or gas. In a form of weight self-control, powerful winds generated by the black hole's feeding frenzy may have cleared out the remaining dust and gas.

Other aspects of black hole growth were uncovered. For example, the typical size of the galaxies undergoing supermassive black hole formation reduces with cosmic time. Such "cosmic downsizing" was previously observed for galaxies undergoing star formation. These results connect well with the observations of nearby galaxies, which find that the mass of a supermassive black hole is proportional to the mass of the central region of its host galaxy.

The other co-authors on the paper in the February 2005 issue of The Astronomical Journal were Len Cowie, Wei-Hao Wang, and Peter Capak (Institute for Astronomy, Univ. of Hawaii), Yuxuan Yang (GSFC and the Univ. of Maryland, College Park), and Aaron Steffen (Univ. of Wisconsin, Madison).

Source

__________________


L

Posts: 131433
Date:
RE: blackhole spectra
Permalink  
 


New observations with the Subaru telescope show that dusty cocoons in galaxies exceptionally bright in infrared light hide supermassive black holes actively ingesting matter. Large amounts of material spiralling into a supermassive black hole more massive than a million suns produces strong radiation. However, if the black hole is buried in dust from all directions, this radiation may not easily be detectable. Although theories suggest that actively radiating supermassive black holes deeply buried in dust outnumber those surrounded by a doughnut-shaped region of dust, so far most black holes detected have been the kind surrounded by a doughnut of dust. A research group led by an astronomer at the National Astronomical Observatory of Japan used the Subaru telescope to perform infrared spectroscopy on galaxies exceptionally bright in the infrared, and found evidence for actively mass accreting super-massive black holes completely surrounded by dust.

In the Universe, there are large numbers of galaxies which are not so bright in visible (optical) light, but radiate strongly in the infrared. The brightest of such galaxies are called "ultraluminous infrared galaxies" (ULIRGs). When taking into account total energy output, ultraluminous infrared galaxies are some of the brightest objects in the Universe. Interestingly, most ultraluminous infrared galaxies appear to be two gas-rich spiral galaxies that have collided and merged. If colliding galaxies contain a lot of gas, as spiral galaxies typically do, the collision can trigger star formation and funnel material into any existing supermassive black hole, both processes that generate large amounts of energy. Although this energy may originate as ultraviolet or visible light, gas is usually accompanied by dust, and the dust absorbs this light and re-emits as heat in the infrared. Once the ultraviolet and visible light is converted to heat, identifying the original energy source becomes an observational challenge.

Although both star formation and the feeding of a black hole can generate large amounts of energy, the source of the energy is very different. Stars generate energy in their cores by nuclear fusion and radiate it into space from their surfaces. When material spirals into a supermassive black hole, material looses gravitational energy, and the lost energy is converted into radiation. This process is called "accretion", and a black hole experiencing accretion is called "active". Since the sources of energy are different, active star-formation and active supermassive black holes are distinguishable relatively easily through optical (visible light) spectroscopy, observations which disperse visible light into many wavelengths or colours, if radiation from the active supermassive blackhole can escape for a large angular range (namely, totally unobscured or obscured by doughnut-shaped dust).

Previous observations show that supermassive black holes with one to ten million solar masses exist at the centre of many galaxies. Many of these black holes are active, and are thought to be surrounded by gas and dust in the shape of a doughnut. However, since ultraluminous infrared galaxies contain a large amount of dust and gas, active supermassive black holes are likely to be obscured in virtually all directions. Such "buried" active supermassive black holes are elusive and have seldom been found observationally, despite theoretical predictions that their number in the Universe is much larger than active supermassive black holes surrounded by doughnut-shaped dust from which ultraviolet and visible light can escape.

An effective way to detect radiation from buried active supermassive black holes is to observe them at wavelengths of light that can penetrate barriers of dust better than ultraviolet or visible light. Infrared light with wavelengths longer than 3 micrometers is such an example, but infrared light from stars and galaxies is usually absorbed by Earth's atmosphere when observing from Earth's surface. However, the summit of Mauna Kea, where the Subaru telescope is located, is so high in elevation (about 4200 meters) that the absorption by Earth's atmosphere of infrared light is minimal at 3-4 micrometers. Mauna Kea is one of the best places in the world to observe faint objects in this wavelength range.

A research group led by Dr. Matatoshi Imanishi from the National Astronomical Observatory of Japan took advantage of this unique opportunity to disentangle a buried active supermassive black hole from active star-formation as the primary energy source of ultraluminous infrared galaxies using infrared 3-4 micrometer spectroscopy. The research group spectroscopically observed nearby (less than two billion light years away from Earth) ultraluminous infrared galaxies at 3-4 micrometers using the instrument IRCS with the Subaru telescope. Thanks to the high sensitivity achieved by the combination of Subaru and IRCS, the research group was able to apply a new energy diagnostic method to reveal signatures of deeply buried active supermassive black holes in a significant fraction of the observed galaxies for the first time. The new observations also confirmed that the active supermassive black holes could account for the bulk of the large infrared luminosities of these galaxies.

A more massive black hole can attract a larger amount of material and can produce brighter radiation. Supermassive black holes with more than ten million solar mass are required to account for the bulk of the brightness of ultraluminous infrared galaxies. When a spiral galaxy, which possesses a supermassive black hole with the mass of one to ten million solar mass, merges with another spiral galaxy, not only do stars form very actively through the collision of gas, expelling a lot of dust to the surrounding interstellar medium, but also the originally existing supermasive black hole(s) can increase its mass by swallowing a large quantity of gas. This research supports the idea that when gas-rich spiral galaxies merge and become ultraluminous infrared galaxies, supermassive black hole(s) can grow up to more than ten million solar masses and produce strong radiation through active mass accretion.

This result was published in the 2006 January 20 issue of Astrophysical Journal .

Source National Astronomical Observatory of Japan

__________________
«First  <  1 2 3 4 5 6  >  Last»  | Page of 6  sorted by
Quick Reply

Please log in to post quick replies.



Create your own FREE Forum
Report Abuse
Powered by ActiveBoard