Galaxies' evolution, influenced by color, luminosity, and clustering

Jan 2, 2007 10:39 GMT  ·  By

A French-Italian team, using VIMOS (the Visible Imager and Multi-Object Spectrograph) on ESO's Very Large Telescope, has found the environments are an important factor modeling the way galaxies form and evolve.

The new technique allowed the researchers to chart for the first time remote parts of the Universe, finding that the distribution of galaxies has considerably evolved with time, depending on the galaxies' surroundings, a surprising discovery for theories of the formation and evolution of galaxies.

The astronomers face a basic question: are the galaxies simply the product of the primordial conditions in which they emerged, or did experiences changed with time?

In a three-year long survey, the team investigated more than 6,500 galaxies over a wide area to see how their properties vary over different timescales, in different surroundings and luminosities, building an atlas of the Universe in three dimensions, going back more than 9 billion years.

The color-density relation changed markedly 7 billion years ago.

The team discovered that the galaxies' luminosity, initial genetic properties, and environments have a main role on their evolution.

"Our results indicate that environment is a key player in galaxy evolution, but there's no simple answer to the 'nature versus nurture' problem in galaxy evolution," said Olivier Le F?vre from the Laboratoire d'Astrophysique de Marseille, France, who coordinates the VIMOS VLT Deep Survey team.

"They suggest that galaxies as we see them today are the product of their inherent genetic information, evolved over time, as well as complex interactions with their environments, such as mergers."

Astronomers have known for several decades that galaxies in the past were different than those in the present-day Universe.

Current galaxies are red, when few or no new stars are being born, or blue, where star formation is active.

A strong correlation has emerged between a galaxy's color and its environment: the red ones tend to be found in dense clusters rather than isolated.

"Using VIMOS, we were able to use the largest sample of galaxies currently available for this type of study, and because of the instrument's ability to study many objects at a time we obtained many more measurements than previously possible," said Angela Iovino, from the Brera Astronomical Observatory, Italy.

Clusters seem to inhibit a galaxy's ability to form stars more quickly compared with those in isolation and bright galaxies also finish their star-forming material earlier than paler ones.

Galaxies' color, luminosity and clustering are not merely a result of primordial conditions 'imprinted' during their formation, but they interact modeling the galaxies' evolution.