Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Monster black holes grow after galactic mergers

11.01.2006


Two new studies show the ’eating habits’ of black holes at the center of young galaxies



An analysis of the Hubble Space Telescope’s deepest view of the universe offers compelling evidence that monster black holes in the centers of galaxies were not born big but grew over time through repeated galactic mergers.

"By studying distant galaxies in the Hubble Ultra Deep Field (HUDF), we have the first statistical evidence that supermassive black-hole growth is linked to the process of galaxy assembly," said Arizona State University astronomer Rogier Windhorst, who is a member of the two teams that conducted the analysis. "Black holes grow by drawing in stars, gas and dust. These morsels come more plentifully within their reach when galaxies merge."


The two teams will present their results in a press conference on Jan. 10 at the 207th meeting of the American Astronomical Society in Washington, D.C.

The HUDF studies also confirm the predictions of recent computer simulations by Lars Hernquist, Philip Hopkins, Tiziana di Matteo and Volker Springel of the Harvard Smithsonian Center for Astrophysics in Cambridge, Mass., that newly merging galaxies are enshrouded in so much dust that astronomers cannot see the black-hole feeding frenzy. The computer simulations, as supported by Hubble, suggest that it takes hundreds of millions to a billion years before enough dust clears so that astronomers can see the black holes feasting on stars and gas from the merger. The telltale sign that black holes are dining is seeing light from galaxies that vary with time.

The two HUDF teams believe they are seeing two distinct phases in galaxy evolution: the first phase -- the tadpole stage -- representing the early-merging systems where central black holes are still enshrouded in dust, and a much later "variable-object phase," in which the merged system has cleared out enough gas for the inner accretion disk around the black hole to become visible.

"The fact that these phases were almost entirely separate was a surprise, because it is commonly believed that galaxy mergers and central black-hole activity are closely related," Windhorst explained. "Our nearby universe, including the Milky Way galaxy in which we live, has mature galaxies, but in order to understand how they formed and evolved, we must study them over time. HUDF provides an actual look back in time to see snapshots of early galaxies so that we can study them when they were young."

A link between the growth of galaxies through mergers and the feeding of the central black holes has long been suspected. The evidence, however, has been inconclusive for many years.

"The HUDF has provided very high-quality information," said Seth Cohen of Arizona State University and leader of one of the teams. "It is the first data we could use to test this theory, since it allowed us to study about 5,000 distant galaxies over a period of four months."

The HUDF observations have now shed light on how the growth of monster black holes kept pace with that of galaxies. A team of astronomers, led by Amber Straughn of Arizona State University, searched the HUDF for "tadpole galaxies," so-called because they have bright knots and tails caused by mergers. These features are produced when the galaxies lose their gravitational grip on their stars, spewing some of those stars into space. The team found about 165 tadpole galaxies, representing about 6 percent of the 2,700 galaxies in the tadpole galaxy study.

"To our surprise, however, these tadpole objects did not show any fluctuation in brightness," Straughn said. "The flickering light -- when it is present -- comes from the material swirling around an accretion disk surrounding a black hole. The material is heated and begins to glow. As it spirals down toward the black hole, it can rapidly change in brightness. This study of tadpole galaxies suggests that black holes in newly merging galaxies are enshrouded in dust, and therefore, we cannot see them accreting material."

Cohen’s team studied the brightness of about 4,600 HUDF objects over several weeks to many months. The Hubble team found that about 45 (non-tadpole) objects, representing 1 percent of the faint galaxies in the study, fluctuated significantly in brightness over time. This result indicates that the galaxies probably contain supermassive black holes that are feeding on stars or gas.

"A black hole’s typical mealtime lasts at least a few dozen million years," Windhorst said. "This is equivalent to black holes spending no more than 15 minutes per day eating all their food -- a veritable fast food diet."

The HUDF analysis also reinforces previous Hubble telescope studies of monster black holes in the centers of nearby, massive galaxies. Those studies showed a close relationship between the mass of a galaxy’s "central bulge" of stars and that of the central black hole. Galaxies today have central black holes with masses ranging from a few million to a few billion solar masses.

Skip Derra | EurekAlert!
Further information:
http://www.asu.edu
http://hubblesite.org/news/2006/04

More articles from Physics and Astronomy:

nachricht Tangled magnetic fields power cosmic particle accelerators
14.12.2018 | DOE/SLAC National Accelerator Laboratory

nachricht In search of missing worlds, Hubble finds a fast evaporating exoplanet
14.12.2018 | NASA/Goddard Space Flight Center

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Data use draining your battery? Tiny device to speed up memory while also saving power

The more objects we make "smart," from watches to entire buildings, the greater the need for these devices to store and retrieve massive amounts of data quickly without consuming too much power.

Millions of new memory cells could be part of a computer chip and provide that speed and energy savings, thanks to the discovery of a previously unobserved...

Im Focus: An energy-efficient way to stay warm: Sew high-tech heating patches to your clothes

Personal patches could reduce energy waste in buildings, Rutgers-led study says

What if, instead of turning up the thermostat, you could warm up with high-tech, flexible patches sewn into your clothes - while significantly reducing your...

Im Focus: Lethal combination: Drug cocktail turns off the juice to cancer cells

A widely used diabetes medication combined with an antihypertensive drug specifically inhibits tumor growth – this was discovered by researchers from the University of Basel’s Biozentrum two years ago. In a follow-up study, recently published in “Cell Reports”, the scientists report that this drug cocktail induces cancer cell death by switching off their energy supply.

The widely used anti-diabetes drug metformin not only reduces blood sugar but also has an anti-cancer effect. However, the metformin dose commonly used in the...

Im Focus: New Foldable Drone Flies through Narrow Holes in Rescue Missions

A research team from the University of Zurich has developed a new drone that can retract its propeller arms in flight and make itself small to fit through narrow gaps and holes. This is particularly useful when searching for victims of natural disasters.

Inspecting a damaged building after an earthquake or during a fire is exactly the kind of job that human rescuers would like drones to do for them. A flying...

Im Focus: Topological material switched off and on for the first time

Key advance for future topological transistors

Over the last decade, there has been much excitement about the discovery, recognised by the Nobel Prize in Physics only two years ago, that there are two types...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

ICTM Conference 2019: Digitization emerges as an engineering trend for turbomachinery construction

12.12.2018 | Event News

New Plastics Economy Investor Forum - Meeting Point for Innovations

10.12.2018 | Event News

EGU 2019 meeting: Media registration now open

06.12.2018 | Event News

 
Latest News

Data use draining your battery? Tiny device to speed up memory while also saving power

14.12.2018 | Power and Electrical Engineering

Tangled magnetic fields power cosmic particle accelerators

14.12.2018 | Physics and Astronomy

In search of missing worlds, Hubble finds a fast evaporating exoplanet

14.12.2018 | Physics and Astronomy

VideoLinks
Science & Research
Overview of more VideoLinks >>>