Overfed Black Holes Shut Down Galactic Star-Making

PASADENA, Calif. -- The Herschel Space Observatory has shown galaxies with the most powerful, active black holes at their cores produce fewer stars than galaxies with less active black holes. The results are the first to demonstrate black holes suppressed galactic star formation when the universe was less than half its current age. Credit: Illustration: NASA/ESA/JPL-Caltech/STScI/R. Hurt (SSC)

Published : May 9, 2012
By JPL

"We want to know how star formation and black hole activity are linked," said Mathew Page of University College London's Mullard Space Science Laboratory in the United Kingdom and lead author of a paper describing these findings in this week's journal Nature. "The two processes increase together up to a point, but the most energetic black holes appear to turn off star formation."

Supermassive black holes, weighing as much as millions of suns, are believed to reside in the hearts of all large galaxies. When gas falls upon these monsters, the material is accelerated and heated around the black hole, releasing great torrents of energy. Earlier in the history of the universe, these giant, luminous black holes, called active galactic nuclei, were often much brighter and more energetic. Star formation was also livelier back then.

Studies of nearby galaxies suggest active black holes can squash star formation. The revved-up, central black holes likely heat up and disperse the galactic reservoirs of cold gas needed to create new stars. These studies have only provided "snapshots" in time, however, leaving the overall relationship of active galactic nuclei and star formation unclear, especially over the cosmic history of galaxy formation.

"To understand how active galactic nuclei affect star formation over the history of the universe, we investigated a time when star formation was most vigorous, between eight and 12 billion years ago," said co-author James Bock, a senior research scientist at NASA's Jet Propulsion Laboratory in Pasadena, Calif., and co-coordinator of the Herschel Multi-tiered Extragalactic Survey. "At that epoch, galaxies were forming stars 10 times more rapidly than they are today on average. Many of these galaxies are incredibly luminous, more than 1,000 times brighter than our Milky Way."

For the new study, Page and colleagues used Herschel data that probed 65 galaxies at wavelengths equivalent to the thickness of several sheets of office paper, a region of the light spectrum known as far-infrared. These wavelengths reveal the rate of star formation, because most of the energy released by developing stars heats surrounding dust, which then re-radiates starlight out in far-infrared wavelengths.

The researchers compared their infrared readings with X-rays streaming from the active central black holes in the survey's galaxies, measured by NASA's Chandra X-ray Observatory. At lower intensities, the black holes' brightness and star formation increased in sync. However, star formation dropped off in galaxies with the most energetic central black holes. Astronomers think inflows of gas fuel new stars and supermassive black holes. Feed a black hole too much, however, and it starts spewing radiation into the galaxy that prevents raw material from coalescing into new stars.

"Now that we see the relationship between active supermassive black holes and star formation, we want to know more about how this process works," said Bill Danchi, Herschel program scientist at NASA Headquarters in Washington. "Does star formation get disrupted from the beginning with the formation of the brightest galaxies of this type, or do all active black holes eventually shut off star formation, and energetic ones do this more quickly than less active ones?"

Herschel is a European Space Agency cornerstone mission, with science instruments provided by consortia of European institutes and important participation by NASA. NASA's Herschel Project Office is based at JPL.

NASA Space Telescopes Reveal Secrets of Supermassive Black Hole

This image of the distant active galaxy Markarian 509 was taken in April 2007 with the Hubble Space Telescope's Wide Field Camera 2.

Credit: NASA, ESA, G. Kriss (STScI), and J. de Plaa (SRON Netherlands Institute for Space Research); Acknowledgment: B. Peterson (Ohio State University)

Published: 29th September, 2011

A fleet of spacecraft including NASA's Hubble Space Telescope has uncovered unprecedented details in the surroundings of a supermassive black hole. Observations reveal huge bullets of gas being driven away from the gravitational monster and a corona of very hot gas hovering above the disk of matter that is falling into the black hole.A team led by Jelle Kaastra of SRON Netherlands Institute for Space Research made use of data from ESA's XMM-Newton and INTEGRAL spacecraft (which study X-rays and gamma rays, respectively), the Hubble Space Telescope (for ultraviolet observations with the COS instrument), and NASA's Chandra (X-ray) Observatory and Swift (gamma-ray) satellites.

The black hole that the team chose to study lies at the heart of the galaxy Markarian 509 (Mrk 509), nearly 500 million light-years away. This black hole is colossal, containing 300 million times the mass of the Sun, and is growing more massive every day as it continues to feed on surrounding matter, which glows brightly as it forms a rotating disk around the black hole. Mrk 509 was chosen because it is known to vary in brightness, which indicates that the flow of matter is turbulent.

The above image of Mrk 509 was taken in April 2007 with Hubble's Wide Field Planetary Camera 2. But using a large number of telescopes that are sensitive to different wavelengths of light gave astronomers unprecedented coverage running from the infrared, through the visible, ultraviolet, X-rays, and into the gamma-ray band.The study is presented in a series of seven papers in the journal Astronomy and Astrophysics, with more expected to be published in coming months.

University of Texas astronomers "Weigh" Heaviest Known Black Hole in our Cosmic Neighborhood

Artist's concept of what a future telescope might see in looking at the black hole at the heart of the galaxy M87. Clumpy gas swirls around the black hole in an accretion disk, feeding the central beast. The black area at center is the black hole itself, defined by the event horizon, beyond which nothing can escape. The bright blue jet shooting from the region of the black hole is created by gas that never made it into the hole itself but was instead funneled into a very energetic jet.

Credit: Gemini Observatory/AURA illustration by Lynette Cook

By McDonald Observatory at University of Texas, Austin —
Published: January 13, 2011

Seattle — Astronomers led by Karl Gebhardt of The University of Texas at Austin have measured the most massive known black hole in our cosmic neighborhood by combining data from a giant telescope in Hawai'i and a smaller telescope in Texas.

The result is an ironclad mass of 6.6 billion suns for the black hole in the giant elliptical galaxy M87. This enormous mass is the largest ever measured for a black hole using a direct technique. Given its massive size, M87 is the best candidate for future studies to "see" a black hole for the first time, rather than relying on indirect evidence of their existence as astronomers have for decades.
The results will be presented in a news conference today at the 217th meeting of the American Astronomical Society in Seattle. Two papers detailing the results will be published soon in The Astrophysical Journal.

Gebhardt, the Herman and Joan Suit Professor of Astrophysics, led a team of researchers using the 8-meter Gemini North telescope in Hawai'i to probe the motions of stars around the black hole in the center of the massive galaxy M87.

University of Texas at Austin graduate student Jeremy Murphy has used the Harlan J. Smith Telescope at the university's McDonald Observatory in West Texas to probe the outer reaches of the galaxy — the so-called "dark halo." The dark halo is a region surrounding the galaxy filled with "dark matter," an unknown type of mass that gives off no light but is detectable by its gravitational effect on other objects.

In order to pin down the black hole's mass conclusively, Gebhardt says, one must account for all the components in the galaxy. Studies of the central and outermost regions of a galaxy are necessary to "see" the influence of the dark halo, the black hole and the stars. But when all of these components are considered together, Gebhardt says, the results on the black hole are definitive, meeting what he calls the "gold standard" for accurately sizing up a black hole.

Gebhardt used the Near-Infrared Field Spectrograph on Gemini to measure the speed of the stars as they orbit the black hole. The study was improved by Gemini's use of "adaptive optics," a system that compensates, in real time, for shifts in the atmosphere that can blur details seen by telescopes on the ground.

Together with the telescope's large collecting area, the adaptive optics system allowed Gebhardt and graduate student Joshua Adams to track the stars at M87's heart with 10 times greater resolution than previous studies.

"The result was only possible by combining the advantages of telescope size and spatial resolution at levels usually restricted to ground and space facilities, respectively," Adams says.

Astronomer Tod Lauer of the National Optical Astronomy Observatory, which was also involved in the Gemini observations, says "our ability to obtain such a robust black hole mass for M87 bodes well for our ongoing efforts to hunt for even larger black holes in galaxies more distant than M87."

Graduate student Jeremy Murphy used a different instrument to track the motions of stars at the outskirts of the galaxy. Studying the stars' movements in these distant regions gives astronomers insight into what the unseen dark matter in the halo is doing. Murphy employed an innovative instrument called VIRUS-P on McDonald Observatory's Harlan J. Smith Telescope.

Studying the distant edges of a galaxy, far from the bright center, is a tricky business, Gebhardt says.

"That has been an enormous struggle for a long time, trying to get what the dark halo is doing at the edge of the galaxy, simply because, when you look there, the stellar light is faint," he says. "This is where the VIRUS-P data comes in, because it can observe such a huge chunk of sky at once."

This means the instrument can add together the faint light from many dim stars and add them together to create one detailed observation. This kind of instrument is called an "integral field unit spectrograph," and VIRUS-P is the world's largest.

"The ability of VIRUS-P to dig deep into the outer halo of M87 and tell us how the stars are moving is impressive," Murphy says. "It has quickly become the leading instrument for this type of work."

The combined Gemini and McDonald data have allowed the team to pinpoint the mass of M87's black hole at 6.6 billion suns. But measuring such a massive black hole is only one step toward a greater goal.

"My ultimate goal is to understand how the stars assembled themselves in a galaxy over time," Gebhardt says.

"How do you make a galaxy? These two datasets probe such an enormous range, in terms of what the mass is in the galaxy. That's the first step to answering this question. It's very hard to understand how the mass accumulates unless you know exactly what's the distribution of mass: how much is in the black hole, how much is in the stars, how much is in the dark halo."

Today's conclusions also hint at another tantalizing possibility for the future: the chance to actually "see" a black hole.

"There's no direct evidence yet that black holes exist," Gebhardt says, "zero, absolutely zero observational evidence. To infer a black hole currently, we choose the 'none of above' option. This is basically because alternative explanations are increasingly being ruled out."

He says the black hole in M87 is so massive that astronomers someday may be able to detect its "event horizon" — the edge of a black hole, beyond which nothing can escape. The event horizon of M87's black hole is about three times larger than the orbit of Pluto — large enough to swallow our solar system whole.

Though the technology does not yet exist, M87's event horizon covers a patch of sky large enough to be imaged by future telescopes. Gebhardt says future astronomers could use a world-wide network of submillimeter telescopes to look for the shadow of the event horizon on a disc of gas that surrounds M87's black hole.

Study confirms supermassive black holes formed before the buildup of galaxies

The dwarf galaxy Henize 2-10, seen in visible light by the Hubble Space Telescope. The central light-pink region shows an area of radio emission seen with the Very Large Array. This area indicates the presence of a supermassive black hole drawing in material from its surroundings. This also is indicated by strong X-ray emission from this region detected by the Chandra X-Ray Observatory. Reines, et al., David Nidever, NRAO/AUI/NSF/NASA

By NRAO, Socorro, New Mexico
Published: January 10, 2011

The surprising discovery of a supermassive black hole in a small nearby galaxy has given astronomers a tantalizing look at how black holes and galaxies may have grown in the early history of the universe. Finding a black hole a million times more massive than the Sun in a star-forming dwarf galaxy is a strong indication that supermassive black holes formed before the buildup of galaxies, the astronomers said.

The galaxy, called Henize 2-10 and located 30 million light-years from Earth, has been studied for years and is forming stars rapidly. Irregularly shaped and about 3,000 light-years across — compared to 100,000 for our own Milky Way — it resembles what scientists think were some of the first galaxies to form in the early universe.

"This galaxy gives us important clues about a very early phase of galaxy evolution that has not been observed before," said Amy Reines from the University of Virginia.

Supermassive black holes lie at the cores of all "full-sized" galaxies. In the nearby universe, there is a direct relationship – a constant ratio — between the masses of the black holes and that of the central "bulges" of the galaxies, leading them to conclude that the black holes and bulges affected each other’s growth.

Two years ago, an international team of astronomers found that black holes in young galaxies in the early universe were more massive than this ratio would indicate. This, they said, was strong evidence that black holes developed before their surrounding galaxies.

"Now, we have found a dwarf galaxy with no bulge at all, yet it has a supermassive black hole. This greatly strengthens the case for the black holes developing first, before the galaxy's bulge is formed," Reines said.

Reines, along with Gregory Sivakoff and Kelsey Johnson from the University of Virginia and the National Radio Astronomy Observatory (NRAO), and Crystal Brogan of the NRAO, observed Henize 2-10 with the National Science Foundation's Very Large Array radio telescope and with the Hubble Space Telescope. They found a region near the center of the galaxy that strongly emits radio waves with characteristics of those emitted by superfast jets of material spewed outward from areas close to a black hole.

They then searched images from the Chandra X-Ray Observatory that showed this same radio-bright region to be strongly emitting an energetic black-hole-powered galactic nucleus.

"Not many dwarf galaxies are known to have massive black holes," Sivakoff said.

While central black holes of roughly the same mass as the one in Henize 2-10 have been found in other galaxies, those galaxies all have much more regular shapes. Henize 2-10 differs not only in its irregular shape and small size, but also in its furious star formation, concentrated in numerous, very dense "super star clusters."

"This galaxy probably resembles those in the very young universe, when galaxies were just starting to form and were colliding frequently. All its properties, including the supermassive black hole, are giving us important new clues about how these black holes and galaxies formed at that time," Johnson said.