'Fossils' of galaxies reveal evolution of super galaxies

London, Sept 29: An international team has observed massive "dead" galaxies in the universe four billion years after the Big Bang which can reveal the formation and evolution of huge galaxies today.

Furthermore, they identified progenitors of these dead galaxies when they were forming stars at an earlier cosmic epoch.

This study establishes a consistent picture of the history of massive galaxies over 11 billion years of cosmic time.

"We would like to explore galaxy evolution in more detail by carrying out an object-by-object study and by extending the method to an even earlier epoch," said Dr. Masato Onodera from Swiss Federal Institute of Technology in Zurich, Switzerland.

In the local universe, massive galaxies hosting more than about 100 billion stars are predominantly dead elliptical galaxies, without any signs of star-formation activity.

The team used Subaru Telescope at the summit of Mauna Kea, Hawaii, to observe multiple objects simultaneously, efficiently observing a sample of 24 faint galaxies.

They created a composite spectrum that would have taken 200 hours of Subaru Telescope's time for a single spectrum of comparable quality.

They discovered that the stellar content of these galaxies is strikingly similar to that of massive elliptical galaxies seen locally.

The analysis shows that the age of the galaxies is already one billion years old when observed four billion years after the Big Bang.

They host 1.7 times more heavy elements relative to the amount of hydrogen.

The results reveal that these massive dead galaxies have evolved without further star formation.

The research was published in The Astrophysical Journal.

IANS