A Space & astronomy forum. SpaceBanter.com

Go Back   Home » SpaceBanter.com forum » Astronomy and Astrophysics » Astronomy Misc
Site Map Home Authors List Search Today's Posts Mark Forums Read Web Partners

Japanese and NASA satellites unveil new type of active galaxy(Forwarded)



 
 
Thread Tools Display Modes
  #1  
Old August 6th 07, 09:36 PM posted to sci.astro
Andrew Yee
external usenet poster
 
Posts: 667
Default Japanese and NASA satellites unveil new type of active galaxy(Forwarded)

Robert Naeye
Goddard Space Flight Center, Greenbelt, Md. July 30, 2007
301-286-4453

RELEASE NO. 07-40

JAPANESE AND NASA SATELLITES UNVEIL NEW TYPE OF ACTIVE GALAXY

GREENBELT, Md. -- An international team of astronomers using NASA's Swift
satellite and the Japanese/U.S. Suzaku X-ray observatory has discovered a
new class of active galactic nuclei (AGN).

By now, you'd think that astronomers would have found all the different
classes of AGN -- extraordinarily energetic cores of galaxies powered by
accreting supermassive black holes. AGN such as quasars, blazars, and
Seyfert galaxies are among the most luminous objects in our Universe,
often pouring out the energy of billions of stars from a region no larger
than our solar system.

But by using Swift and Suzaku, the team has discovered that a relatively
common class of AGN has escaped detection ... until now. These objects are
so heavily shrouded in gas and dust that virtually no light gets out.

"This is an important discovery because it will help us better understand
why some supermassive black holes shine and others don't,"
says astronomer and team member Jack Tueller of NASA's Goddard Space
Flight Center in Greenbelt, Md.

Evidence for this new type of AGN began surfacing over the past two years.
Using Swift's Burst Alert Telescope (BAT), a team led by Tueller has found
several hundred relatively nearby AGNs that were previously missed because
their visible and ultraviolet light was smothered by gas and dust. The BAT
was able to detect high-energy X-rays from these heavily blanketed AGNs
because, unlike visible light, high-energy X-rays can punch through thick
gas and dust.

To follow up on this discovery, Yoshihiro Ueda of Kyoto University, Japan,
Tueller, and a team of Japanese and American astronomers targeted two of
these AGNs with Suzaku. They were hoping to determine whether these
heavily obscured AGNs are basically the same type of objects as other AGN,
or whether they are fundamentally different. The AGNs reside in the
galaxies ESO 005-G004 and ESO 297-G018, which are about 80 million and 350
million light-years from Earth, respectively.

Suzaku covers a broader range of X-ray energies than BAT, so astronomers
expected Suzaku to see X-rays across a wide swath of the X-ray spectum.
But despite Suzaku's high sensitivity, it detected very few low- or
medium-energy X-rays from these two AGN, which explains why previous X-ray
AGN surveys missed them.

According to popular models, AGNs are surrounded by a donut-shaped ring of
material, which partially obscures our view of the black hole. Our viewing
angle with respect to the donut determines what type of object we see. But
team member Richard Mushotzky, also at NASA Goddard, thinks these newly
discovered AGN are completely surrounded by a shell of obscuring material.
"We can see visible light from other types of AGN because there is
scattered light," says Mushotzky. "But in these two galaxies, all the
light coming from the nucleus is totally blocked."

Another possibility is that these AGN have little gas in their vicinity.
In other AGN, the gas scatters light at other wavelengths, which makes the
AGN visible even if they are shrouded in obscuring material.

"Our results imply that there must be a large number of yet unrecognized
obscured AGNs in the local universe," says Ueda.

In fact, these objects might comprise about 20 percent of point sources
comprising the X-ray background, a glow of X-ray radiation that pervades
our Universe. NASA's Chandra X-ray Observatory has found that this
background is actually produced by huge numbers of AGNs, but Chandra was
unable to identify the nature of all the sources.

By missing this new class, previous AGN surveys were heavily biased, and
thus gave an incomplete picture of how supermassive black holes and their
host galaxies have evolved over cosmic history. "We think these black
holes have played a crucial role in controlling the formation of galaxies,
and they control the flow of matter into clusters," says Tueller. "You
can't understand the universe without understanding giant black holes and
what they're doing. To complete our understanding we must have an unbiased
sample."

The discovery paper will appear in the August 1st issue of the
Astrophysical Journal Letters.

For related images on this story, please visit:

http://www.nasa.gov/centers/goddard/...ive_galaxy.htm

More information about Swift can be found at:
http://swift.gsfc.nasa.gov

More information about Suzaku can be found at:
http://suzaku.gsfc.nasa.gov


 




Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Japanese and NASA satellites unveil new type of active galaxy (Forwarded) Andrew Yee[_1_] News 0 August 6th 07 08:45 PM
ASTRO: NGC 6028 Another Hoag's Object type ring galaxy Rick Johnson[_2_] Astro Pictures 2 June 27th 07 07:27 PM
NOAA satellites ready for active hurricane season (Forwarded) Andrew Yee[_1_] News 0 June 22nd 07 03:34 PM
NASA GeneSat Shows Small Satellites Can Deliver Big Science (Forwarded) Andrew Yee News 0 January 14th 07 12:14 AM
Delivery of the Glonass navigation system satellites by the DM-type Jacques van Oene News 0 December 28th 04 05:45 PM


All times are GMT +1. The time now is 10:17 PM.


Powered by vBulletin® Version 3.6.4
Copyright ©2000 - 2024, Jelsoft Enterprises Ltd.
Copyright ©2004-2024 SpaceBanter.com.
The comments are property of their posters.