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




STELLAR CHEMISTRY
Assembling The Most Massive Galaxies In The Universe
by Staff Writers
Zurich, Switzerland (SPX) Aug 27, 2008


File image.

Astronomers have caught multiple massive galaxies in the act of merging about 4 billion years ago. This discovery, made possible by combining the power of the best ground- and space-based telescopes, uniquely supports the favoured theory of how galaxies form.

How do galaxies form? The most widely accepted answer to this fundamental question is the model of 'hierarchical formation', a step-wise process in which small galaxies merge to build larger ones. One can think of the galaxies forming in a similar way to how streams merge to form rivers, and how these rivers, in turn, merge to form an even larger river.

This theoretical model predicts that massive galaxies grow through many merging events in their lifetime. But when did their cosmological growth spurts finish? When did the most massive galaxies get most of their mass?

To answer these questions, astronomers study massive galaxies in clusters, the cosmological equivalent of cities filled with galaxies.

"Whether the brightest galaxies in clusters grew substantially in the last few billion years is intensely debated. Our observations show that in this time, these galaxies have increased their mass by 50%," says Kim-Vy Tran from the University of Zurich, Switzerland, who led the research.

The astronomers made use of a large ensemble of telescopes and instruments, including ESO's Very Large Telescope (VLT) and the Hubble Space Telescope, to study in great detail galaxies located 4 billion light-years away. These galaxies lie in an extraordinary system made of four galaxy groups that will assemble into a cluster.

In particular, the team took images with VIMOS and spectra with FORS2, both instruments on the VLT. From these and other observations, the astronomers could identify a total of 198 galaxies belonging to these four groups.

The brightest galaxies in each group contain between 100 and 1000 billion of stars, a property that makes them comparable to the most massive galaxies belonging to clusters.

"Most surprising is that in three of the four groups, the brightest galaxy also has a bright companion galaxy. These galaxy pairs are merging systems," says Tran.

The brightest galaxy in each group can be ordered in a time sequence that shows how luminous galaxies continue to grow by merging until recently, that is, in the last 5 billion years. It appears that due to the most recent episode of this 'galactic cannibalism', the brightest galaxies became at least 50% more massive.

This discovery provides unique and powerful validation of hierarchical formation as manifested in both galaxy and cluster assembly.

"The stars in these galaxies are already old and so we must conclude that the recent merging did not produce a new generation of stars," concludes Tran. "Most of the stars in these galaxies were born at least 7 billion years ago."

The team is composed of Kim-Vy H. Tran (Institute for Theoretical Physics, University of Zurich, Switzerland), John Moustakas (New York University, USA), Anthony H. Gonzalez and Stefan J. Kautsch (University of Florida, Gainesville, USA), and Lei Bai and Dennis Zaritsky (Steward Observatory, University of Arizona, USA). The results presented here are published in the Astrophysical Journal Letters: "The Late Stellar Assembly Of Massive Cluster Galaxies Via Major Merging", by Tran et al.

.


Related Links
Institute for Theoretical Physics, University of Zurich
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
XMM-Newton's Massive Discovery
Paris, France (ESA) Aug 26, 2008
ESA's orbiting X-ray observatory XMM-Newton has discovered the most massive cluster of galaxies seen in the distant Universe until now. The galaxy cluster is so big that there can only be a handful of them at that distance, making this a rare catch indeed. The discovery confirms the existence of dark energy. The newly-discovered monster, known only by the catalogue number 2XMM J083026+5241 ... read more


STELLAR CHEMISTRY
NASA Seeks Input For Commercial Lunar Communications And Navigation

China's First Lunar Probe Satellite Normal After Eclipse

A Flash Of Insight: LCROSS Mission Update

India Postpones First Lunar Mission Until Mid-October

STELLAR CHEMISTRY
Seeing Mars In A Particle Of Dust

NASA's Mars Rover Opportunity Climbing Out Of Crater

Ice Cold Sunrise On Mars

Phoenix Digs Deeper As Third Month Nears End

STELLAR CHEMISTRY
Ares Progress Report For August

Elegant Resorts And Virgin Galactic Make Space Travel A Reality

Going Looney In Space

Iran To Send First Astronaut Into Space Within 10 Years

STELLAR CHEMISTRY
China to launch Venezuela's first satellite: Chavez

China's Space Ambitions

Rocket For China's Manned Space Mission At Launch Center

China To Release 700 Hours Of Chang'e-1 Data

STELLAR CHEMISTRY
ISS Program Facing Hard Choices

US-Russia chill threatens NASA space program

ISS Orbit Adjustment Complete

ISS Crew Inspired By Vision And Dreams Of Jules Verne

STELLAR CHEMISTRY
Arianespace To Launch Koreasat 6

Inmarsat Selects ILS Proton To Launch S-Band Satellite For Europe

Forecast International Projects 50 Billion Dollar ELV Market

Successful Launch For Third Inmarsat-4 Satellite

STELLAR CHEMISTRY
Universally Speaking, Earthlings Share A Nice Neighborhood

An Interstellar Mission Scenario

Computer Simulations Show How Special The Solar System Is

Twinkle, Twinkle Alien Ocean

STELLAR CHEMISTRY
Key Advance Toward Micro-Spacecraft

MIT's Lincoln Lab Upgrades Sputnik-Era Antenna

GMV Releases Hifly 6 Satellite Control System

New Metamaterials Bend Light Backwards




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