Subscribe free to our newsletters via your
. 24/7 Space News .




STELLAR CHEMISTRY
Most Quasars Live on Snacks, Not Large Meals
by Staff Writers
Pasadena CA (JPL) Jun 22, 2012


The galaxies pictured here have so much dust surrounding them that the brilliant light from their quasars cannot be seen in these images NASA's Hubble Space Telescope. Quasars are the brilliant beacons of light that are powered by black holes feasting on captured material, and in the process, heating some of the matter to millions of degrees. Image credit: NASA/ESA/Yale. For a larger version of this image please go here.

Black holes in the early universe needed a few snacks rather than one giant meal to fuel their quasars and help them grow, according to observations from NASA's Spitzer and Hubble space telescopes.

Quasars are the brilliant beacons of light that are powered by black holes feasting on captured material, and in the process, heating some of the matter to millions of degrees. The brightest quasars reside in galaxies distorted by collisions with other galaxies. These encounters send lots of gas and dust into the gravitational whirlpool of hungry black holes.

Now, however, astronomers are uncovering an underlying population of fainter quasars that thrive in normal-looking spiral galaxies. They are triggered by black holes snacking on such tasty treats as a batch of gas or the occasional small satellite galaxy.

A census of 30 quasar host galaxies conducted with two of NASA's premier observatories, Hubble and Spitzer, has found that 26 of the host galaxies bear no telltale signs of collisions with neighbors, such as distorted shapes. Only one galaxy in the sample shows evidence of an interaction with another galaxy. The galaxies existed roughly 8 billion to 12 billion years ago, during a peak epoch of black-hole growth.

The study, led by Kevin Schawinski of Yale University, New Haven, Conn., bolsters evidence that the growth of most massive black holes in the early universe was fueled by small, long-term events rather than dramatic short-term major mergers.

"Quasars that are products of galaxy collisions are very bright," Schawinski said. "The objects we looked at in this study are the more typical quasars. They're a lot less luminous. The brilliant quasars born of galaxy mergers get all the attention because they are so bright and their host galaxies are so messed up. But the typical bread-and-butter quasars are actually where most of the black-hole growth is happening. They are the norm, and they don't need the drama of a collision to shine."

Schawinski's science paper has been accepted for publication in a letter to the Monthly Notices of the Royal Astronomical Society.

For his analysis, Schawinski analyzed galaxies observed by the Spitzer and Hubble telescopes in the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey.

He chose 30 dust-enshrouded galaxies that appeared extremely bright in infrared images taken by the Spitzer telescope, a sign that their resident black holes are feasting on surrounding material. The dust is blocking the quasar's light at visible wavelengths. But infrared light pierces the dust, allowing Schawinski to study the galaxies' detailed structure. The masses of those galaxies are comparable to that of our Milky Way.

Schawinski then studied the galaxies in near-infrared images taken by Hubble's Wide Field Camera 3. Hubble's sharp images allowed careful analysis of galaxy shapes, which would be significantly distorted if major galaxy mergers had taken place and were disrupting the structure. Instead, in all but one instance, the galaxies show no such disruption.

Whatever process is stoking the quasars, it's below the detection capability of even Hubble. "I think it's a combination of processes, such as random stirring of gas, supernovae blasts, swallowing of small bodies, and streams of gas and stars feeding material into the nucleus," Schawinski said.

A black hole doesn't need much gas to satisfy its hunger and turn on a quasar. "There's more than enough gas within a few light-years from the center of our Milky Way to turn it into a quasar," Schawinski explained. "It just doesn't happen. But it could happen if one of those small clouds of gas ran into the black hole. Random motions and stirrings inside the galaxy would channel gas into the black hole. Ten billion years ago, those random motions were more common and there was more gas to go around. Small galaxies also were more abundant and were swallowed up by larger galaxies."

The galaxies in Schawinski's study are prime targets for NASA's upcoming James Webb Space Telescope, a large infrared observatory scheduled to launch later this decade. "To get to the heart of what kinds of events are powering the quasars in these galaxies, we need the Webb telescope. Hubble and Spitzer have been the trailblazers for finding them."

The team of astronomers in this study consists of K. Schawinski, B.D. Simmons, C.M. Urry and E. Glikman (Yale University), and E. Treister (Universidad de Concepcion, Chile).

.


Related Links
Spitzer at Caltech
Spitzer at NASA
Stellar Chemistry, The Universe And All Within It






Comment on this article via your Facebook, Yahoo, AOL, Hotmail login.

Share this article via these popular social media networks
del.icio.usdel.icio.us DiggDigg RedditReddit GoogleGoogle








STELLAR CHEMISTRY
Chance Alignment Between Galaxies Mimics a Cosmic Collision
Baltimore MD (SPX) Jun 22, 2012
Because of the alignment, NGC 3314B's dust lanes appear lighter than those of NGC 3314A. This is not because that galaxy lacks dust, but rather because its dust lanes are lightened by the bright fog of stars in the foreground. NGC 3314A's dust, in contrast, is backlit by the stars of NGC 3314B, silhouetting them against the bright background. The color composite was produced from exposures ... read more


STELLAR CHEMISTRY
Researchers Estimate Ice Content of Crater at Moon's South Pole

Researchers find evidence of ice content at the moon's south pole

Nanoparticles found in moon glass bubbles explain weird lunar soil behaviour

UA Lunar-Mining Team Wins National Contest

STELLAR CHEMISTRY
Orbiter Out of Precautionary 'Safe Mode'

Researchers calculate size of particles in Martian clouds of CO2 snow

ESA tests self-steering rover in 'Mars' desert

Opportunity Faces Slow Going Due To Communication Issues

STELLAR CHEMISTRY
Complex Challenges Solved In Tech Meetings For Commercial Crew Program

Boeing Completes Key Reviews of Space Launch System

Two NASA Visualizations Selected for Computers Graphics Showcase

NASA technology-sharing portal announced

STELLAR CHEMISTRY
That's No Lab, It's a Space Station

China to conduct first manual space docking

Designer elaborates on challenges facing Shenzhou-9 mission

Rocket Scientist Who 'Spied for China' Freed

STELLAR CHEMISTRY
Did You Say 1.2 Billion Particles Per Month?

Varied Views from the ISS

Strange Geometry - Yes, It's All About the Math

Capillarity in Space - Then and Now, 1962-2012

STELLAR CHEMISTRY
A milestone in launcher preparations for Arianespace's fourth Ariane 5 flight of 2012

US military launches new satellite into space

NASA Administrator Bolden Views Historic SpaceX Dragon Capsule

NASA's NuSTAR Mission Lifts Off

STELLAR CHEMISTRY
Where Are The Metal Worlds And Is The Answer Blowing In The Wind

Metal-poor stars are rich with small planets

Astronomers spy 2 planets in tight quarters as they orbit a distant star

Astronomers with NASA's Kepler Mission find 'puzzling pair of planets'

STELLAR CHEMISTRY
Study: Handwriting in decline with tech

E-book trend slow at US libraries: study

Samsung launches new phone in US, taking on Apple

China defends rare earths policy




The content herein, unless otherwise known to be public domain, are Copyright 1995-2014 - Space Media Network. AFP, UPI and IANS news wire stories are copyright Agence France-Presse, United Press International and Indo-Asia News Service. ESA Portal Reports are copyright European Space Agency. All NASA sourced material is public domain. Additional copyrights may apply in whole or part to other bona fide parties. Advertising does not imply endorsement,agreement or approval of any opinions, statements or information provided by Space Media Network on any Web page published or hosted by Space Media Network. Privacy Statement