Featured Research

from universities, journals, and other organizations

"Nearby" Galaxy Clusters May Still Be Birthing New Stars

Date:
June 10, 1998
Source:
Northwestern University
Summary:
Astronomers at Northwestern University have found newer, bluer galaxies than expected in nearby galaxy clusters, suggesting broods of young stars in these galaxies.

Astronomers at Northwestern University have found newer, bluer galaxies than expected in nearby galaxy clusters, suggesting broods of young stars in these galaxies. The finding, presented at the American Astronomical Society annual meeting in San Diego, shows that star formation from galactic gas and dust in these clusters has occurred much more recently than astronomers had thought -- and may in fact be an ongoing process.

Clusters of galaxies are gravitationally bound groups of about 1000 galaxies about 3 million light years across, with a combined mass 10,000 times the mass of our own Milky Way galaxy.

"The model of galaxy evolution in clusters is that 4 billion to 5 billion years ago, clusters had many more blue galaxies than clusters do today," said Melville P. Ulmer, professor of physics and astronomy at Northwestern, who led the study. The blueness, he explained, is caused by younger, hotter stars.

"If you look at clusters of galaxies far away, which means a long time ago, on average they have a lot more blue galaxies than red galaxies," Ulmer said. "When you look nearby, you find clusters of galaxies have hardly any blue galaxies. They're almost all red galaxies."

But Ulmer and an undergraduate student, Anne J. Metevier, and postdoctoral researcher A. Katherine Romer focused on three clusters only 2 billion light years away. Although the universe was perhaps 80 percent as old as it is now when light left these clusters, these particular nearby clusters nevertheless appeared "young" because their X-ray pattern was still in the shape of two blobs rather than a fully formed sphere. Clusters emit X-rays from hot, ionized gas between their galaxies.

"The shape of the X-ray emissions led us to believe these clusters might still be forming, and the galaxies within them might be young as well," said Metevier, who is now in graduate study at the University of California, Santa Cruz. This turned out to be true, she said, as evidenced by the color of the clusters. In fact, one of the three clusters Ulmer's group studied is the bluest galaxy cluster ever.

"This cluster is remarkable not only because it is so blue but because until now astronomers believed that blue clusters could only exist at early times in the universe, yet this cluster is nearly a contemporary of our own," Ulmer said.

The belief that the galaxy population in clusters varies smoothly from blue (young) to old (red) as we change our view from distant to nearby clusters is called the Butcher-Oemler effect and may now have to be revised.

"What we think is happening is that these particular clusters we've looked at are just forming, and in the process of coalescing , some gas gets compressed," Ulmer said. "When the gas is compressed on the galaxies, that ignites star formation." The result is bluer galaxies within the cluster.

The optical observations were made by Romer on the Nation Science Foundation's National Optical Astronomy Observatory's 36-inch telescope on Kitt Peak in Arizona. The X-ray observations were made with NASA's Einstein Satellite. Romer is now at Carnegie Mellon University.

Ulmer said researchers now need to measure the fraction of blue galaxies in other clusters at a range of distances from 1 billion to 5 billion light years away, paying special attention to those clusters with a clumpy appearance in their X-ray images. Further insights into cluster formation and its link to galaxy formation, he said, may come from new, high quality X-ray images from NASA's Advanced X-ray Astrophysics Facility, scheduled for launch in December.

The reported work was supported in part by as NASA Space Grant to the State of Illinois, the NASA Astrophysics Data Program, Northwestern University, Carnegie Mellon University and the University of California, Santa Cruz.


Story Source:

The above story is based on materials provided by Northwestern University. Note: Materials may be edited for content and length.


Cite This Page:

Northwestern University. ""Nearby" Galaxy Clusters May Still Be Birthing New Stars." ScienceDaily. ScienceDaily, 10 June 1998. <www.sciencedaily.com/releases/1998/06/980610211611.htm>.
Northwestern University. (1998, June 10). "Nearby" Galaxy Clusters May Still Be Birthing New Stars. ScienceDaily. Retrieved August 29, 2014 from www.sciencedaily.com/releases/1998/06/980610211611.htm
Northwestern University. ""Nearby" Galaxy Clusters May Still Be Birthing New Stars." ScienceDaily. www.sciencedaily.com/releases/1998/06/980610211611.htm (accessed August 29, 2014).

Share This




More Space & Time News

Friday, August 29, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Experiment Tests Whether Universe Is Actually A Hologram

Experiment Tests Whether Universe Is Actually A Hologram

Newsy (Aug. 27, 2014) Researchers at Fermilab are using a device called "The Holometer" to test whether our universe is actually a 2-D hologram that just seems 3-D. Video provided by Newsy
Powered by NewsLook.com
SpaceX’s Falcon 9 Rocket Explodes After Liftoff

SpaceX’s Falcon 9 Rocket Explodes After Liftoff

Newsy (Aug. 23, 2014) The private spaceflight company says it is preparing a thorough investigation into Friday's mishap. Video provided by Newsy
Powered by NewsLook.com
Did Russia Really Find Plankton On The ISS? NASA Not So Sure

Did Russia Really Find Plankton On The ISS? NASA Not So Sure

Newsy (Aug. 21, 2014) Russian cosmonauts say they've found evidence of sea plankton on the International Space Station's windows. NASA is a little more skeptical. Video provided by Newsy
Powered by NewsLook.com
Space to Ground: Hello Georges

Space to Ground: Hello Georges

NASA (Aug. 18, 2014) Europe's ATV-5 delivers new science and the crew tests smart SPHERES. Questions or comments? Use #spacetoground to talk to us. Video provided by NASA
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins