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




TIME AND SPACE
Mysterious quasar sequence explained
by Staff Writers
Pasadena, CA (SPX) Sep 12, 2014


New work solves a quasar mystery that astronomers have been puzzling over for 20 years. It shows that most observed quasar phenomena can be unified with two simple quantities: one that describes how efficiently the hole is being fed, and the other that reflects the viewing orientation of the astronomer. This graph shows the distribution of about 20,000 luminous Sloan Digital Sky Survey quasars in the two-dimensional space of broad line width versus FeII strength, color-coded by the strength of the narrow [OIII] line emission. The strong horizontal trend is the main sequence of quasars driven by the efficiency of the black hole accretion, while the vertical spread of broad line width is largely due to our viewing angle to the inner region of the quasar. Image courtesy Yue Shen. For a larger versionh of this image please go here.

Quasars are supermassive black holes that live at the center of distant massive galaxies. They shine as the most luminous beacons in the sky across the entire electromagnetic spectrum by rapidly accreting matter into their gravitationally inescapable centers. New work from Carnegie's Hubble Fellow Yue Shen and Luis Ho of the Kavli Institute for Astronomy and Astrophysics (KIAA) at Peking University solves a quasar mystery that astronomers have been puzzling over for 20 years.

Their work, published in the September 11 issue of Nature, shows that most observed quasar phenomena can be unified with two simple quantities: one that describes how efficiently the hole is being fed, and the other that reflects the viewing orientation of the astronomer.

Quasars display a broad range of outward appearances when viewed by astronomers, reflecting the diversity in the conditions of the regions close to their centers. But despite this variety, quasars have a surprising amount of regularity in their quantifiable physical properties, which follow well-defined trends (referred to as the "main sequence" of quasars) discovered more than 20 years ago. Shen and Ho solved a two-decade puzzle in quasar research: What unifies these properties into this main sequence?

Using the largest and most-homogeneous sample to date of over 20,000 quasars from the Sloan Digital Sky Survey, combined with several novel statistical tests, Shen and Ho were able to demonstrate that one particular property related to the accretion of the hole, called the Eddington ratio, is the driving force behind the so-called main sequence.

The Eddington ratio describes the efficiency of matter fueling the black hole, the competition between the gravitational force pulling matter inward and the luminosity driving radiation outward. This push and pull between gravity and luminosity has long been suspected to be the primary driver behind the so-called main sequence, and their work at long last confirms this hypothesis.

Of additional importance, they found that the orientation of an astronomer's line-of-sight when looking down into the black hole's inner region plays a significant role in the observation of the fast-moving gas innermost to the hole, which produces the broad emission lines in quasar spectra.

This changes scientists' understanding of the geometry of the line-emitting region closest to the black hole, a place called the broad-line region: the gas is distributed in a flattened, pancake-like configuration. Going forward, this will help astronomers improve their measurements of black hole masses for quasars.

"Our findings have profound implications for quasar research. This simple unification scheme presents a pathway to better understand how supermassive black holes accrete matter and interplay with their environments," Shen said.

"And better black hole mass measurements will benefit a variety of applications in understanding the cosmic growth of supermassive black holes and their place in galaxy formation," Ho added.

.


Related Links
Carnegie Institution
Understanding Time and Space






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








TIME AND SPACE
NASA's RXTE Satellite Decodes the Rhythm of an Unusual Black Hole
Washington DC (SPX) Aug 19, 2014
Astronomers have uncovered rhythmic pulsations from a rare type of black hole 12 million light-years away by sifting through archival data from NASA's Rossi X-ray Timing Explorer (RXTE) satellite. The signals have helped astronomers identify an unusual midsize black hole called M82 X-1, which is the brightest X-ray source in a galaxy known as Messier 82. Most black holes formed by dying st ... read more


TIME AND SPACE
Year's final supermoon is a Harvest Moon

China Aims for the Moon, Plans to Bring Back Lunar Soil

Electric Sparks May Alter Evolution of Lunar Soil

China to test recoverable moon orbiter

TIME AND SPACE
Flash-Memory Reformat Successful

NASA's Mars Curiosity rover reaches 'far frontier'

NASA's Mars Curiosity Rover Arrives at Martian Mountain

Flash-Memory Reformat On Opportunity Underway

TIME AND SPACE
The long descent

NASA's Orion Spacecraft Nears Completion, Ready for Fueling

Top trends at IFA 2014, Europe's biggest gadget fair

Tech giants bet on 'smart home' revolution

TIME AND SPACE
China eyes working with other nations as station plans develop

China completes construction of advanced space launch facility

China to launch second space lab in 2016: official

China's Space Station is Still On Track

TIME AND SPACE
4th SpaceX Cargo Mission to ISS Dragon Scheduled for Sep 20

Three Russian and American astronauts return to Earth

Science Continues on Orbital Lab While Trio Prepares for Departure

International Space Station accidentally launches satellites on its own

TIME AND SPACE
NASA's Wind-Watching ISS-RapidScat Ready for Launch

Proton Launches May Compete on Price With US Falcons

SpaceX's next cargo launch set for Sept 20

MEASAT-3b and Optus 10 given go-ahead for Ariane 5 Sept 11 launch

TIME AND SPACE
Solar System Simulation Reveals Planetary Mystery

'Hot Jupiters' provoke their own host suns to wobble

First evidence for water ice clouds found outside solar system

NRL Scientist Explores Birth of a Planet

TIME AND SPACE
Not just cool - it's a gas

Where to grab space debris

Grooving Crystal Surfaces Repel Water

U.S. military taps Northrop Grumman for new technology




The content herein, unless otherwise known to be public domain, are Copyright 1995-2014 - Space Media Network. All websites are published in Australia and are solely subject to Australian law and governed by Fair Use principals for news reporting and research purposes. AFP, UPI and IANS news wire stories are copyright Agence France-Presse, United Press International and Indo-Asia News Service. ESA news 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 All images and articles appearing on Space Media Network have been edited or digitally altered in some way. Any requests to remove copyright material will be acted upon in a timely and appropriate manner. Any attempt to extort money from Space Media Network will be ignored and reported to Australian Law Enforcement Agencies as a potential case of financial fraud involving the use of a telephonic carriage device or postal service.