Scientists discover ancient galaxies that are still forming stars

Published: Thursday, August 19, 2010, 16:54 [IST]
 

Washington, Aug 19 (ANI): Astronomers from Texas A and M have discovered a significant fraction of ancient galaxies that are still actively forming stars.

Dr. Kim-Vy Tran and her team used NASA's Spitzer Space Telescope to discover that a high-redshift cluster known as CLG J02182-05102, shockingly "modern" in its appearance and size despite being observed just 4 billion years after the Big Bang, still produces hundreds to thousands of new stars every year.

The stellar birthrate is higher in the cluster's center than at the cluster's edges-the exact opposite of what happens in our local portion of the Universe, where the cores of galaxy clusters are known to be galactic graveyards full of massive elliptical galaxies composed of old stars.

"There are more star-forming galaxies in the field than in the crowded cores of galaxy clusters. However, in our cluster, we find many galaxies with star-formation rates comparable to their cousins in the lower-density field environment," said Tran.

Exactly why this star power increases as galaxies become more crowded remains a mystery.

Tran thinks the densely populated surroundings could lead to galaxies triggering activity in one another, or that all galaxies were extremely active when the Universe was young.

Astronomers can now focus on understanding why massive assemblies of galaxies transition from very active to passive.

"Our study shows that by looking farther into the distant Universe, we have revealed the missing link between the active galaxies and the quiescent behemoths that live in the local Universe," Tran added.

Tran will continue to examine these clusters more thoroughly and hopefully to understand why they are still so energetic.

"We will also start looking at several more distant galaxy clusters to see if we find similar behaviour," she said.

The team's findings are detailed in their paper, "Reversal of Fortune:Confirmation of an Increasing Star Formation-Density Relation in a Cluster at z=1.62." (ANI)

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