Featured Research

from universities, journals, and other organizations

Ultra-compact dwarf galaxies are bright star clusters

Date:
December 19, 2011
Source:
Astronomy & Astrophysics
Summary:
A new statistical study sheds light on the so-called 'ultra-compact dwarf galaxies' (UCDs). A team of astronomers has investigated how many of these UCDs exist in nearby galaxy clusters and groups. They show that the properties of UCDs match those of bright star clusters.

Stellar systems in the Fornax cluster: galaxies, globular clusters, and UCDs.
Credit: Background image is from Arna Karick (Oxford, UK) using the Michigan Curtis Schmidt Telescope at CTIO (digital color composite/mosaic in B, V and I bands).

Astronomy & Astrophysics is publishing the results of a detailed investigation of how many 'ultra-compact dwarf galaxies' (UCDs) can be found in nearby galaxy clusters. UCDs were recognized as a populous and potentially distinct class of stellar systems about a decade ago. But they are still mysterious objects that are characterized by a compact morphology (30-300 light-years in size) and high masses (more than one million solar masses).

More generally, their properties (e.g., their size, shape, or luminosity) are similar to those of both star clusters and dwarf galaxies. Several hundred UCDs have been found to date. Two main formation channels for these puzzling objects have been proposed so far. UCDs might either be very massive star clusters or be 'normal' dwarf galaxies transformed by tidal effects.

S. Mieske, M. Hilker, and I. Misgeld (ESO) present a statistical study of the UCD population: they define new statistical tools that relate the number of UCDs to the total luminosity of their host environment. This allows them to use statistical arguments to test the hypothesis that UCDs are bright star clusters. They predict that if UCDs are bright star clusters, we would expect to find only one or two UCDs around the Milky Way, which corresponds to what is seen, as omega Centauri is the only Milky Way satellite that can be considered a UCD.

With their new tools at hand, the authors have investigated the results of spectroscopic UCD surveys in the environment of massive galaxy clusters such as Fornax, Hydra, and Centaurus, as well as in galaxy groups like our very own Local Group. Most data analysed were obtained at ESO's Very Large Telescope in Chile, using the instruments FLAMES, VIMOS, and FORS2. For the Fornax cluster, they also used a large database of compact stellar objects, which contained about 180 UCDs.

This statistical study clearly shows that the luminosity distribution of UCDs match very well that of the brightest globular star clusters. It supports the hypothesis that the vast majority of UCDs are actually very massive star clusters. From a statistical point of view, there is no need to invoke another scenario to explain the origin of UCDs.


Story Source:

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


Journal Reference:

  1. S. Mieske, M. Hilker, I. Misgeld. The specific frequencies of ultra-compact dwarf galaxies. Astronomy & Astrophysics, 2011; 537: A3 DOI: 10.1051/0004-6361/201117634

Cite This Page:

Astronomy & Astrophysics. "Ultra-compact dwarf galaxies are bright star clusters." ScienceDaily. ScienceDaily, 19 December 2011. <www.sciencedaily.com/releases/2011/12/111219102052.htm>.
Astronomy & Astrophysics. (2011, December 19). Ultra-compact dwarf galaxies are bright star clusters. ScienceDaily. Retrieved September 2, 2014 from www.sciencedaily.com/releases/2011/12/111219102052.htm
Astronomy & Astrophysics. "Ultra-compact dwarf galaxies are bright star clusters." ScienceDaily. www.sciencedaily.com/releases/2011/12/111219102052.htm (accessed September 2, 2014).

Share This




More Space & Time News

Tuesday, September 2, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Raw: NASA Captures Solar Flare

Raw: NASA Captures Solar Flare

AP (Sep. 1, 2014) NASA reported the sun emitted a mid-level solar flare, on August 24th. NASA's Solar Dynamics Observatory captured the images of the flare, which erupted on the left side of the sun. (Sept. 1) Video provided by AP
Powered by NewsLook.com
Space Shuttle Discovery's Legacy, 30 Years Later

Space Shuttle Discovery's Legacy, 30 Years Later

Newsy (Aug. 30, 2014) The space shuttle Discovery launched for the very first time 30 years ago. Here's a look back at its legacy. Video provided by Newsy
Powered by NewsLook.com
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

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