Posted on by Tammy Plotner

Emerging Supermassive Black Holes Choke Star Formation

The LABOCA camera on the ESO-operated 12-metre Atacama Pathfinder Experiment (APEX) telescope reveals distant galaxies undergoing the most intense type of star formation activity known, called a starburst. This image shows these distant galaxies, found in a region of sky known as the Extended Chandra Deep Field South, in the constellation of Fornax (The Furnace). The galaxies seen by LABOCA are shown in red, overlaid on an infrared view of the region as seen by the IRAC camera on the Spitzer Space Telescope. Credit: ESO, APEX (MPIfR/ESO/OSO), A. Weiss et al., NASA Spitzer Science Center

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Located on the Chajnantor plateau in the foothills of the Chilean Andes, ESO’s APEX telescope has been busy looking into deep, deep space. Recently a group of astronomers released their findings regarding massive galaxies in connection with extreme times of star formation in the early Universe. What they found was a sharp cut-off point in stellar creation, leaving “massive – but passive – galaxies” filled with mature stars. What could cause such a scenario? Try the materialization of a supermassive black hole…

By integrating data taken with the LABOCA camera on the ESO-operated 12-metre Atacama Pathfinder Experiment (APEX) telescope with measurements made with ESO’s Very Large Telescope, NASA’s Spitzer Space Telescope and other facilities, astronomers were able to observe the relationship of bright, distant galaxies where they form into clusters. They found that the density of the population plays a major role – the tighter the grouping, the more massive the dark matter halo. These findings are the considered the most accurate made so far for this galaxy type.

Located about 10 billion light years away, these submillimetre galaxies were once home to starburst events – a time of intense formation. By obtaining estimations of dark matter halos and combining that information with computer modeling, scientists are able to hypothesize how the halos expanding with time. Eventually these once active galaxies settled down to form giant ellipticals – the most massive type known.

“This is the first time that we’ve been able to show this clear link between the most energetic starbursting galaxies in the early Universe, and the most massive galaxies in the present day,” says team leader Ryan Hickox of Dartmouth College, USA and Durham University, UK.

However, that’s not all the new observations have uncovered. Right now there’s speculation the starburst activity may have only lasted around 100 million years. While this is a very short period of cosmological time, this massive galactic function was once capable of producing double the amount of stars. Why it should end so suddenly is a puzzle that astronomers are eager to understand.

“We know that massive elliptical galaxies stopped producing stars rather suddenly a long time ago, and are now passive. And scientists are wondering what could possibly be powerful enough to shut down an entire galaxy’s starburst,” says team member Julie Wardlow of the University of California at Irvine, USA and Durham University, UK.

Right now the team’s findings are offering up a new solution. Perhaps at one point in cosmic history, starburst galaxies may have clustered together similar to quasars… locating themselves in the same dark matter halos. As one of the most kinetic forces in our Universe, quasars release intense radiation which is reasoned to be fostered by central black holes. This new evidence suggests intense starburst activity also empowers the quasar by supplying copious amounts of material to the black hole. In response, the quasar then releases a surge of energy which could eradicate the galaxy’s leftover gases. Without this elemental fuel, stars can no longer form and the galaxy growth comes to a halt.

“In short, the galaxies’ glory days of intense star formation also doom them by feeding the giant black hole at their centre, which then rapidly blows away or destroys the star-forming clouds,” explains team member David Alexander from Durham University, UK.

Original Story Source: European Southern Observatory News. For Further Reading: Research Paper Link.

Posted on by Jason Major

First-Ever Image of a Black Hole to be Captured by Earth-Sized Scope

Spitzer telescope view of the galactic center. (NASA/JPL-Caltech/S. Stolovy)

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“Sgr A* is the right object, VLBI is the right technique, and this decade is the right time.”

So states the mission page of the Event Horizon Telescope, an international endeavor that will combine the capabilities of over 50 radio telescopes across the globe to create a single Earth-sized telescope to image the enormous black hole at the center of our galaxy. For the first time, astronomers will “see” one of the most enigmatic objects in the Universe.

And tomorrow, January 18, researchers from around the world will convene in Tucson, AZ to discuss how to make this long-standing astronomical dream a reality.

During a conference organized by Dimitrios Psaltis, associate professor of astrophysics at the University of Arizona’s Steward Observatory, and Dan Marrone, an assistant professor of astronomy at the Steward Observatory, astrophysicists, scientists and researchers will gather to coordinate the ultimate goal of the Event Horizon Telescope; that is, an image of Sgr A*’s accretion disk and the “shadow” of its event horizon.

“Nobody has ever taken a picture of a black hole. We are going to do just that.”

– Dimitrios Psaltis, associate professor of astrophysics at the University of Arizona’s Steward Observatory

Sgr A* (pronounced as “Sagittarius A-star”) is a supermassive black hole residing at the center of the Milky Way. It is estimated to contain the equivalent mass of 4 million Suns, packed into an area smaller than the diameter of Mercury’s orbit.

Because of its proximity and estimated mass, Sgr A* presents the largest apparent event horizon size of any black hole candidate in the Universe. Still, its size in the sky is about the same as viewing “a grapefruit on the Moon.”

So what are astronomers expecting to actually “see”?

(Read more: What does a black hole look like?)

A black hole's "shadow", or event horizon. (NASA illustration)

Because black holes by definition are black – that is, invisible in all wavelengths of radiation due to the incredibly powerful gravitational effect on space-time around them – an image of the black hole itself will be impossible. But Sgr A*’s accretion disk should be visible to radio telescopes due to its billion-degree temperatures and powerful radio (as well as submillimeter, near infrared and X-ray) emissions… especially in the area leading up to and just at its event horizon. By imaging the glow of this super-hot disk astronomers hope to define Sgr A*’s Schwarzschild radius – its gravitational “point of no return”.

This is also commonly referred to as its shadow.

The position and existence of Sgr A* has been predicted by physics and inferred by the motions of stars around the galactic nucleus. And just last month a giant gas cloud was identified by researchers with the European Southern Observatory, traveling directly toward Sgr A*’s accretion disk. But, if the EHT project is successful, it will be the first time a black hole will be directly imaged in any shape or form.

“So far, we have indirect evidence that there is a black hole at the center of the Milky Way,” said Dimitrios Psaltis. “But once we see its shadow, there will be no doubt.”

(Read more: Take a trip into our galaxy’s core)

Submillimeter Telescope on Mt. Graham, AZ. (Used with permission from University of Arizona, T. W. Folkers, photographer.)

The ambitious Event Horizon Telescope project will use not just one telescope but rather a combination of over 50 radio telescopes around the world, including the Submillimeter Telescope on Mt. Graham in Arizona, telescopes on Mauna Kea in Hawaii and the Combined Array for Research in Millimeter-wave Astronomy in California, as well as several radio telescopes in Europe, a 10-meter dish at the South Pole and, if all goes well, the 50-radio-antenna capabilities of the new Atacama Large Millimeter Array in Chile. This coordinated group effort will, in effect, turn our entire planet into one enormous dish for collecting radio emissions.

By using long-term observations with Very Long Baseline Interferometry (VLBI) at short (230-450 GHz) wavelengths, the EHT team predicts that the goal of imaging a black hole will be achieved within the next decade.

“What is great about the one in the center of the Milky Way is that is big enough and close enough,” said assistant professor Dan Marrone. “There are bigger ones in other galaxies, and there are closer ones, but they’re smaller. Ours is just the right combination of size and distance.”

Read more about the Tucson conference on the University of Arizona’s news site here, and visit the Event Horizon Telescope project site here.

 

Posted on by Ray Sanders

Does Starburst Activity Starve Galaxies of Gas?

The Southern Cross, the Milky Way, and the Large Magellanic Cloud shine above the Atacama Large Millimeter/submillimeter Array (ALMA) as it observes on a clear night sky during its Early Science phase. Image credit: C. Padilla, NRAO/AUI/NSF

[/caption]Using the partially constructed ALMA observatory, a group of astronomers have found new evidence that helps explain how young, star-forming galaxies end up as ‘red and dead’ elliptical galaxies.

According to current galactic evolution theories, mergers of spiral galaxies are thought to explain why nearby elliptical galaxies have few young stars. Merging galaxies direct gas and dust into starburts, which are regions of rapid star formation, as well as into the central supermassive black hole at the core of the merging galaxies. As matter is piled onto a black hole, powerful jets erupt, and the region becomes a brightly shining quasar. Eventually the powerful jets emanating from the central black hole push away any potentially star-forming gas, which causes the starbursts to cease.


Astronomers have, until recently, been unable to detect enough mergers at the “jet” stage to make a definite link between the outflows and the end of starburst activity. During early science observations in 2011, ALMA became the first telescope to confirm almost two dozen galaxies at the critical, yet brief stage of galaxy evolution.

“Despite ALMA’s great sensitiviy to detecting starbursts, we saw nothing, or next to nothing – which is exactly what we hoped it would see,” said Dr. Carol Lonsdale (NRAO). Lonsdale presented the findings at the American Astronomical Society’s meeting in Austin, Texas on behalf of an international team of astronomers.

ALMA was set to look for the signature of dust warmed by star-forming regions. Half of Lonsdale’s two dozen galaxies were not visible in ALMA’s observations, and the other half very dim.

“ALMA’s results reveal to us that there is little-to-no starbursting going on in these young, active galaxies. The galaxy evolution model says this is thanks to their central black holes whose jets are starving them of star-forming gas,” Lonsdale said. “On its first run out of the gate, ALMA confirmed a critical phase in the timeline of galaxy evolution.”

Infographic showing the sequence of events that model a typical galaxy becoming a so-called "red and dead" elliptical. Lonsdale and her team found a large population of galaxies, right in the middle of this sequence, between steps d and e. Image Credit: Hopkins, et al., NOAO/AURA/NSF.

After the star-forming gas is blown away, merging galaxies no longer form new stars. Once the massive, bright, blue, and short-lived stars die out, the redder, longer-lived, lower mass stars begin to dominate the population, leading to a gas-starved galaxy taking on a redder hue. To support the gas-starvation theory, astronomers needed to observe the process at work, specifically in merging galaxies with high power jets where quasars can be found.

Lonsdale added, “The missing phase had to be among quasars that could be seen brightly in infrared and radio wavelengths — mergers young enough to have their cores still swaddled in infrared-bright dust, but old enough that their black holes were well fed and producing jets observable in the radio.”

The team’s hunt for the specific type of quasars began with NASA’s Wide-field Infrared Survey Explorer (WISE) spacecraft. The WISE data consists of millions of objects in its all-sky survey of the Universe. Lonsdale led WISE’s quasar survey team that picked out the brightest, reddest objects this infrared telescope had mapped.

Selected images from among the twenty-three quasars observed with ALMA so far in its hunt for candidate starving galaxies. Image Credit: C. Lonsdale, NRAO/AUI/NSF; ALMA (NRAO/ESO/NAOJ)

Lonsdale and her team compared the WISE data against the NRAO’s VLA Sky Survey of 1.8 million radio objects. The team then used results common to both sets of data to determine the best targets for their starburst search with ALMA. Since ALMA uses longer infrared wavelengths than WISE, Lonsdale’s team was able to make the distinction between dust warmed by starburst activity and dust heated by material falling onto the central black hole.

There are 26 more WISE quasars for ALMA to survey before Lonsdale and her team publish their results. In the meantime, Lonsdale and her team will observe these galaxies with the newly re-named Karl G. Jansky Very Large Array (VLA).

“ALMA revealed to us this rare stage of galaxy starvation, and now we want to use the VLA to focus on delineating the outflows that robbed these galaxies of their fuel,” Lonsdale said. “Together, the two most sensitive radio telescope arrays in the world will help us truly understand the fate of spiral galaxies like our own Milky Way.”

If you’d like to learn more about the Atacama Large Millimeter/Submillimeter Array (ALMA), visit: https://almascience.nrao.edu/about-alma/alma-site

Source: NRAO Press Release

Posted on by Tammy Plotner

Dodging Black Hole Bullets

This 327-MHz radio view of the center of our galaxy highlights the position of the black hole system H1743-322, as well as other features. (Credit: J. Miller-Jones, ICRAR-Curtin Univ.; C. Brogan, NRAO)

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In mid-2009 a binary star system cataloged as H H1743–322 shot off something very unusual. Poised about 28,000 light years distant in the direction of the constellation of Scorpius, this rather ordinary system made up of a normal star and unknown mass black hole was busy exchanging mass. The pair orbits in mere days with a stream of material flowing continuously between them. This gas causes a flat accretion disk measuring millions of miles across to form and it is centered on the black hole. As the matter twirls toward the center, it becomes compressed and heats to tens of millions of degrees, spitting out X-rays… and bullets.

Utilizing data from NASA’s Rossi X-ray Timing Explorer (RXTE) satellite and the National Science Foundation’s (NSF) Very Long Baseline Array (VLBA) radio telescope, an international team of astronomers were able to confirm the moment a black hole located within our galaxy fired a super speedy clump of gas into surrounding space. Blasting forth at about one-quarter the speed of light, these “bullets” of ionized gas are hypothesized to have originated from an area just outside the black hole’s event horizon.

“Like a referee at a sports game, we essentially rewound the footage on the bullets’ progress, pinpointing when they were launched,” said Gregory Sivakoff of the University of Alberta in Canada. He presented the findings today at the American Astronomical Society meeting in Austin, Texas. “With the unique capabilities of RXTE and the VLBA, we can associate their ejection with changes that likely signaled the start of the process.”

As we have learned, some of the matter headed toward the center of a black hole can be ejected from the accretion disk as opposing twin jets. For the most part, these jets are a constant stream of particles, but can sometimes form into strong “outflows” which get spit out – rapid fire – as gaseous blobs. In early June 2009, H1743–322 did just that… and astronomers were on hand observing with RXTE, the VLBA, the Very Large Array near Socorro, N.M., and the Australia Telescope Compact Array (ATCA) near Narrabri in New South Wales. During this time they were able to confirm the happenings through X-ray and radio data. From May 28 to June 2, things were nominal “though RXTE data show that cyclic X-ray variations, known as quasi-periodic oscillations or QPOs, gradually increased in frequency over the same period” and by June 4th, ATCA verified that activity had pretty much sloughed off. By June 5th, even the QPOs were gone.

Then it happened…

On the same day that everything went totally quiet, H1743–322 fired off a bullet! Radio emissions jumped and a highly accurate and detailed VLBA image disclosed a energetic missile of gas blasting forth along a jet trajectory. The very next day a second bullet took out in the opposite direction. But this wasn’t the curious part of the event… It was the timing. Up to this point, researchers speculated that a radio outburst accompanied the firing of the gas bullet, but VLBA information showed they were launched around 48 hours in advance of the major radio flare. This information will be published in the Monthly Notices of the Royal Astronomical Society.

Radio imaging by the Very Long Baseline Array (top row), combined with simultaneous X-ray observations by NASA's RXTE (middle), captured the transient ejection of massive gas "bullets" by the black hole binary H1743-322 during its 2009 outburst. By tracking the motion of these bullets with the VLBA, astronomers were able to link the ejection event to the disappearance of X-ray signals seen in RXTE data. These signals, called quasi-periodic oscillations (QPOs), vanished two days earlier than the onset of the radio flare that astronomers previously had assumed signaled the ejection. (Credit: NRAO and NASA's Goddard Space Flight Center)

“This research provides new clues about the conditions needed to initiate a jet and can guide our thinking about how it happens,” said Chris Done, an astrophysicist at the University of Durham, England, who was not involved in the study.

These are just mini-ammo compared to what happens in the center of an active galaxy. They don’t just fire bullets – they blast off cannons. A massive black hole weighing in a millions to billions of times the mass of the Sun can shoot off its load across millions of light years!

“Black hole jets in binary star systems act as fast-forwarded versions of their galactic-scale cousins, giving us insights into how they work and how their enormous energy output can influence the growth of galaxies and clusters of galaxies,” said lead researcher James Miller-Jones at the International Center for Radio Astronomy Research at Curtin University in Perth, Australia.

Original Story Source: NASA News Feature.

Posted on by Tammy Plotner

In The Still Of The Night… Listening To The “Heartbeat” Of A Tiny Black Hole

Artist's rendering showing the jet fully established. Credit: NASA/Goddard Space Flight Center/CI Lab

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Is everything quiet in deep space?  Not hardly.  It’s a place jammed with noises of all kinds.  So much noise, in fact, that it could be quite difficult to pick up a faint signature of something small…  something like the smallest black hole known.  Thanks to  NASA’s Rossi X-ray Timing Explorer (RXTE) , an international team of astronomers have found the pulse they were looking for and it’s a pattern that’s only been seen in one other black hole system.

Its name is IGR J17091-3624 and it’s a binary system which consists of a normal star and a black hole with a mass that measures only about three times solar.  In theoretical terms, that’s right at the edge where possibility of being a black hole begins.

Here’s the picture…  In this binary system, escaping gas from the “normal” star flows across space in the direction of the black hole.  This action creates a disk where friction heats it to millions of degrees – releasing X-rays.  Periodic changes in the strength of the X-ray emissions point towards the actions taking place within the gas disk.  Scientists theorize that fast changes occur at the event horizon… the point of no return.

IGR J17091-3624 was discovered when it went into outburst in 2003. Current observations have it becoming active every few years and its most recent flare began in February of this year and has been kicking up cosmic dust ever since. Observations place it in the general direction of Scorpius, but astronomers aren’t sure of an exact distance – somewhere between 16,000 light years to more than 65,000. However, IGR J17091-3624 isn’t absolutely alone in its unique changes. Black hole binary, GRS 1915+105, also displays a number of well-ordered rhythms, too.

This animation compares the X-ray ‘heartbeats’ of GRS 1915 and IGR J17091, two black holes that ingest gas from companion stars. GRS 1915 has nearly five times the mass of IGR J17091, which at three solar masses may be the smallest black hole known. A fly-through relates the heartbeats to hypothesized changes in the black hole’s jet and disk. Credit: NASA/Goddard Space Flight Center/CI Lab

“We think that most of these patterns represent cycles of accumulation and ejection in an unstable disk, and we now see seven of them in IGR J17091,” said Tomaso Belloni at Brera Observatory in Merate, Italy. “Identifying these signatures in a second black hole system is very exciting.”

Binary GRS 1915 has some very cool characteristics.  Right now astronomers have observed jets blasting out in opposite directions cruising along at 98% the speed of light.  These originate at the event horizon where strong magnetic fields fuel them and each pulsation matches the occurrence of the jets. By observing the X-ray spectrum with RXTE, researchers have discovered the interior of the disk creates enough radiation to halt the gas flow – an outward wind which negates the inward flow – and shuts down activity.  As a result, the inner disk glows hot and bright, eliminating itself as it flows toward the black hole and kick starts the jet activity again.  It’s a process that happens in as little as 40 seconds!

Right now astronomers aren’t able to prove that IGR J17091 has a particle jet, but the regular pulsations indicate it. Records show this “heartbeat” occurs about every five seconds – about 8 times faster than its counterpart and some 20 times more faint. Numbers like this would make it a very tiny black hole.

“Just as the heart rate of a mouse is faster than an elephant’s, the heartbeat signals from these black holes scale according to their masses,” said Diego Altamirano, an astrophysicist at the University of Amsterdam in The Netherlands and lead author of a paper describing the findings in the November 4 issue of The Astrophysical Journal Letters. It’s just the beginning of a full scale program involving RXTE to compare information from both black holes.  Even more detailed data will be added from NASA’s Swift satellite and XMM-Newton, too.

“Until this study, GRS 1915 was essentially a one-off, and there’s only so much we can understand from a single example,” said Tod Strohmayer, the project scientist for RXTE at NASA’s Goddard Space Flight Center in Greenbelt, Md. “Now, with a second system exhibiting similar types of variability, we really can begin to test how well we understand what happens at the brink of a black hole.”

Original Story Source: NASA Mission News

Posted on by Jason Major

First Look at a Black Hole’s Feast


A true heart of darkness lies at the center of our galaxy: Sagittarius A* (pronounced “A-star”) is a supermassive black hole with the mass of four million suns packed into an area only as wide as the distance between Earth and the Sun. Itself invisible to direct observation, Sgr A* makes its presence known through its effect on nearby stars, sending them hurtling through space in complex orbits at speeds upwards of 600 miles a second. And it emits a dull but steady glow in x-ray radiation, the last cries of its most recent meals. Gas, dust, stars… solar systems… anything in Sgr A*’s vicinity will be drawn inexorably towards it, getting stretched, shredded and ultimately absorbed (for lack of a better term) by the dark behemoth, just adding to its mass and further strengthening its gravitational pull.

Now, for the first time, a team of researchers led by Reinhard Genzel from the Max-Planck Institute for Extraterrestrial Physics in Germany will have a chance to watch a supermassive black hole’s repast take place.

Continue reading “First Look at a Black Hole’s Feast”

Posted on by Ray Sanders

Looking at Early Black Holes with a ‘Time Machine’

The large scale cosmological mass distribution in the simulation volume of the MassiveBlack. The projected gas density over the whole volume ('unwrapped' into 2D) is shown in the large scale (background) image. The two images on top show two zoom-in of increasing factor of 10, of the regions where the most massive black hole - the first quasars - is formed. The black hole is at the center of the image and is being fed by cold gas streams. Image Courtesy of Yu Feng.

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What fed early black holes enabling their very rapid growth? A new discovery made by researchers at Carnegie Mellon University using a combination of supercomputer simulations and GigaPan Time Machine technology shows that a diet of cosmic “fast food” (thin streams of cold gas) flowed uncontrollably into the center of the first black holes, causing them to be “supersized” and grow faster than anything else in the Universe.

When our Universe was young, less than a billion years after the Big Bang, galaxies were just beginning to form and grow. According to prior theories, black holes at that time should have been equally small. Data from the Sloan Digital Sky Survey has shown evidence to the contrary – supermassive black holes were in existence as early as 700 million years after the Big Bang.

“The Sloan Digital Sky Survey found supermassive black holes at less than 1 billion years. They were the same size as today’s most massive black holes, which are 13.6 billion years old,” said Tiziana Di Matteo, associate professor of physics (Carnegie Mellon University). “It was a puzzle. Why do some black holes form so early when it takes the whole age of the Universe for others to reach the same mass?”

Supermassive black holes are the largest black holes in existence – weighing in with masses billions of times that of the Sun. Most “normal” black holes are only about 30 times more massive than the Sun. The currently accepted mechanism for the formation of supermassive black holes is through galactic mergers. One problem with this theory and how it applies to early supermassive black holes is that in early Universe, there weren’t many galaxies, and they were too distant from each other to merge.

Rupert Croft, associate professor of physics (Carnegie Mellon University) remarked, “If you write the equations for how galaxies and black holes form, it doesn’t seem possible that these huge masses could form that early, But we look to the sky and there they are.”

In an effort to understand the processes that formed the early supermassive black holes, Di Matteo, Croft and Khandai created MassiveBlack – the largest cosmological simulation to date. The purpose of MassiveBlack is to accurately simulate the first billion years of our universe. Describing MassiveBlack, Di Matteo remarked, “This simulation is truly gigantic. It’s the largest in terms of the level of physics and the actual volume. We did that because we were interested in looking at rare things in the universe, like the first black holes. Because they are so rare, you need to search over a large volume of space”.

Croft and the team started the simulations using known models of cosmology based on theories and laws of modern day physics. “We didn’t put anything crazy in. There’s no magic physics, no extra stuff. It’s the same physics that forms galaxies in simulations of the later universe,” said Croft. “But magically, these early quasars, just as had been observed, appear. We didn’t know they were going to show up. It was amazing to measure their masses and go ‘Wow! These are the exact right size and show up exactly at the right point in time.’ It’s a success story for the modern theory of cosmology.”

The data from MassiveBlack was added to the GigaPan Time Machine project. By combining the MassiveBlack data with the GigaPan Time Machine project, researchers were able to view the simulation as if it was a movie – easily panning across the simulated universe as it formed. When the team noticed events which appeared interesting, they were also able to zoom in to view the events in greater detail than what they could see in our own universe with ground or space-based telescopes.

When the team zoomed in on the creation of the first supermassive black holes, they saw something unexpected. Normal observations show that when cold gas flows toward a black hole it is heated from collisions with other nearby gas molecules, then cools down before entering the black hole. Known as ‘shock heating’, the process should have stopped early black holes from reaching the masses observed. Instead, the team observed thin streams of cold dense gas flowing along ‘filaments’ seen in large-scale surveys that reveal the structure of our universe. The filaments allowed the gas to flow directly into the center of the black holes at incredible speed, providing them with cold, fast food. The steady, but uncontrolled consumption provided a mechanism for the black holes to grow at a much faster rate than their host galaxies.

The findings will be published in the Astrophysical Journal Letters.

If you’d like to read more, check out the papers below ( via Physics arXiv ):
Terapixel Imaging of Cosmological Simulations
The Formation of Galaxies Hosting z~6 Quasars
Early Black Holes in Cosmological Simulations
Cold Flows and the First Quasars

Learn more about Gigapan and MassiveBlack at: http://gigapan.org/gigapans/76215/ and http://www.psc.edu/science/2011/supermassive/

Source: Carnegie Mellon University Press Release

Posted on by Amy Shira Teitel

Astronomers Find the Most Supermassive Black Holes Yet

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For years, astronomer Karl Gebhardt and graduate student Jeremy Murphy at The University of Texas at Austin have been hunting for black holes — the dense concentration of matter at the centre of galaxies. Earlier this year, they made a record-breaking discovery. They found a black hole weighing 6.7 billion times the mass of our Sun in the centre of the galaxy M87.

But now they shattered their own record. Combining new data from multiple observations, they’ve found not one but two supermassive black holes that each weigh as much as 10 billion Suns.

“They just keep getting bigger,” Gebhardt said.

An artist's impression of the black hole at the centre of the M87 galaxy. Image credit: Gemini Observatory/AURA illustration by Lynette Cook

Black holes are made of extremely densely packed matter. They produce such a strong gravitational field that even light cannot escape. Because they can’t be seen directly, astronomers find black holes by plotting the orbits of stars around these giant invisible masses. The shape and size of these stars’ orbits can determine the mass of the black hole.

Exploding stars called supernovae often leave behind black holes, but these only weigh as much as the single star. Black holes billions of times the mass of our Sun have grown to be so big. Most likely, an ordinary black hole consumed another, captured huge numbers of stars and the massive amount of gas that they contain, or be the result of two galaxies colliding. The larger the collision, the more massive the black hole.

The supermassive black holes Gebhardt and Murphy have found are at the centres of two galaxies more than 300 million light years from Earth. One weighing 9.7 billion solar masses is located in the elliptical galaxy NGC 3842, the brightest galaxy in the Leo cluster of galaxies 320 million light years away in the direction of the constellation Leo. The other is as large or larger and sits in the elliptical galaxy NGC 4889, the brightest galaxy in the Coma cluster about 336 million light years from Earth in the direction of the constellation Coma Berenices.

Each of these black holes has an event horizon — the point of no return where nothing, not even light can escape their gravity — 200 times larger than the orbit of Earth (or five times the orbit of Pluto). That’s a mind-boggling 29,929,600,000 kilometres or 18,597,391,235 miles. Beyond the event horizon, each has a gravitational influence that extends over 4,000 light years in every direction.

The illustration shows the relationship between the mass of a galaxy's central black hole and the mass of its central bulge. Recent discoveries of supermassive black holes may mean that the black holes in all nearby massive galaxies are more massive than we think. This could signal a change in our understanding of the relationship between a black hole and its surrounding galaxy. Image credit: Tim Jones/UT-Austin after K. Cordes & S. Brown (STScI)

For comparison, the black hole at the centre of our Milky Way Galaxy has an event horizon only one-fifth the orbit of Mercury — about 11,600,000 kilometres or 7,207,905 miles. These supermassive black holes are 2,500 times more massive than our own.

Gebhardt and Murphy found the supermassive black holes by combining data from multiple sources. Observations from the Gemini and Keck telescopes revealed the smallest, innermost parts of these galaxies while data from the George and Cynthia Mitchell Spectrograph on the 2.7-meter Harlan J. Smith Telescope revealed their largest, outmost regions.

Putting everything together to deduce the black holes’ mass was a challenge. “We needed computer simulations that can accommodate such huge changes in scale,” Gebhardt said. “This can only be done on a supercomputer.”

But the payoff doesn’t end with finding these massive galactic centre. The discovery has much more important implications. It “tells us something fundamental about how galaxies form” Gebhardt said.

These black holes could be the dark remnants of previously bright galaxies called quasars. The early universe was full of quasars, some thought to have been powered by black holes 10 billion Solar masses or more. Astronomers have been wondering where these supermassive galactic centres have since disappeared to.

Gebhardt and Murphy might have found a key piece in solving the mystery. Their two supermassive black holes might shed light on how black holes and their galaxies have interacted since the early universe. They may be a missing link between ancient quasars and modern supermassive black holes.

Source: McDonald Observatory Press Release.

Where Have All the Quasars Gone?

Posted on by Ray Sanders

Astronomers Discover Ancient ‘Ultra-Red’ Galaxies

This artist's conception portrays four extremely red galaxies that lie almost 13 billion light-years from Earth. Discovered using the Spitzer Space Telescope, these galaxies appear to be physically associated and may be interacting. One galaxy shows signs of an active galactic nucleus, shown here as twin jets streaming out from a central black hole. Image Credit: David A. Aguilar (CfA)

[/caption]A team of astronomers, led by Jiasheng Huang (Harvard-Smithsonian Center for Astrophysics) using the Spitzer Space Telescope, have discovered four ‘Ultra-Red’ galaxies that formed when our Universe was about a billion years old. Huang and his team used several computer models in an attempt to understand why these galaxies appear so red, stating, “We’ve had to go to extremes to get the models to match our observations.”

The results of Huang’s research were recently published in The Astrophysical Journal

Using the Spitzer Space Telescope helped make the discovery possible, as it is more sensitive to infrared light than other space telescopes such as the Hubble. The newly discovered galaxies are sixty times brighter in the infrared than they are at the longest/reddest wavelengths HST can detect.

What processes are at work to create these extremely red objects, and why are they of interest to astronomers?

There are several reasons a galaxy could be reddened. For starters, extremely distant galaxies can have their light “redshifted” due to the expansion of the universe. If a galaxy contains large amounts of dust, it will also appear redder than a galaxy with less dust. Lastly, older galaxies will tend to be redder, due to a higher concentration of old, red stars and less younger bluer stars.

According to the paper, Huang and his team created three models to determine why these galaxies appear so red. Of their models, the one which suggests an old stellar population is currently the best fit to the observations. Supporting this conclusion, co-author Giovanni Fazio stated, “Hubble has shown us some of the first protogalaxies that formed, but nothing that looks like this. In a sense, these galaxies might be a ‘missing link’ in galactic evolution”.

Studying these extremely distant galaxies helps provide astronomers with a better understanding of the early universe, specifically how early galaxies formed and what conditions were present when some of the first stars were created. The next step in understanding these “ERO” galaxies is to obtain an accurate redshift for the galaxies, by using more powerful telescopes such as the Large Millimeter Telescope or Atacama Large Millimeter Array.

Huang and his team have plans to search for more galaxies similar to the four recently discovered by his team. Huang’s co-author Giovanni Fazio adds, “There’s evidence for others in other regions of the sky. We’ll analyze more Spitzer and Hubble observations to track them down.”

If you’d like to learn more, you can access the full paper (via arXiv.org) at: http://arxiv.org/pdf/1110.4129v1

Source: Harvard-Smithsonian Center for Astrophysics press release , arxiv.org

Posted on by Gemma Lavender

Astronomers Complete the Puzzle of Black Hole Description

The optical image on the left, from the Digitized Sky Survey, shows Cygnus X-1 outlined in a red box located near large active regions of star formation in the Milky Way that spans 700 light-years across. An artist’s illustration on the right depicts what astronomers believe is happening within the Cygnus X-1 system with the black hole pulling material from a massive, blue companion star. This material forms a disk (shown in red and orange) that rotates around the black hole before falling into it or being directed away in the form of powerful jets. Credit: X-ray: NASA/CXC; Optical: Digitized Sky Survey.

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Light may not be able to escape a black hole, but now enough information has escaped one black hole’s clutches that astronomers have, for the first time, been able to provide a complete description of it. A team of astronomers from the Harvard-Smithsonian Center for Astrophysics (CfA) and San Diego State University have made the most accurate measurements ever of X-ray binary system Cygnus X-1, allowing them to unravel the longstanding mysteries of its black hole and to retrace its history since its birth around six million years ago.

Cygnus X-1, which consists of a black hole that is drawing material from its massive blue companion star, was found to be emitting powerful X-rays nearly half a century ago. Since its discovery in 1964, this galactic X-ray source has been intensely scrutinized with astronomers attempting to gain information about its mass and spin. But without an accurate measurement of its distance from the Earth, which has been estimated to be between 5,800 and 7,800 light-years, we could only imagine what secrets Cygnus X-1 was harboring.

Astronomer Mark Reid of CfA led his team to garner the most accurate measurement of the distance to Cygnus X-1 with the help of the National Science Foundation’s Very Long Baseline Array (VLBA), a continent-wide radio-telescope system. The team locked down a direct trigonometric measurement of 6,070 light-years.

“Because no other information can escape a black hole, knowing its mass, spin and electrical charge gives a complete description of it,” says Reid who is a co-author of three papers on Cygnus X-1, published in the Astrophysical Journal Letters (available here, here, and here). “The charge of this black hole is nearly zero, so measuring its mass and spin make our description complete.”

Using their new precise distance measurement along with the Chandra X-ray Observatory, the Rossi X-ray Timing Explorer, the Advanced Satellite for Cosmology and Astrophysics and visible-light observations made over more than two decades, the team pieced together the “No Hair” theorem – the complete description that Reid speaks of – by revealing a hefty mass of nearly 15 solar masses and a turbo spin speed of 800 revolutions per second. “We now know that Cygnus X-1 is one of the most massive stellar black holes in the Milky Way,” says Jerry Orosz of San Diego State University, also an author of the paper with Reid and Lijun Gou of the CfA. “It’s spinning as fast as any black hole we’ve ever seen.”

As an added bonus, observations using the VLBA back in 2009 and 2010 had also measured Cygnus X-1’s movement through the galaxy leading scientists to the conclusion that it is much too slow to have been produced by the explosion of a supernova and without evidence of a large “kick” at birth, astronomers believe that it may have resulted from the dark collapse of a progenitor star with a mass greater than about 100 times the mass of the Sun that got lost in a vigorous stellar wind. “There are suggestions that this black hole could have formed without a supernova explosion and our results support those suggestions,” says Reid.

It seems that with these measurements, Professor Stephen Hawking has well and truly had to eat his own words after placing a bet with fellow astrophysicist Kip Thorne, a professor of theoretical physics at the California Institute of Technology, that Cygnus X-1 did not contain a black hole.

“For forty years, Cygnus X-1 has been the iconic example of a black hole. However, despite Hawking’s concession, I have never been completely convinced that it really does contain a black hole – until now,” says Thorne. “The data and modeling in these three papers at last provide a completely definitive description of this binary system.”

Sources: CfA