Dead Galaxies: Star-Formation Learnings

In an observation of long-dead galaxies, a team led by Swiss Federal Institute of Technology, in Zurich, recently looked at systems of stars held together by gravity that were dead 4 billion years after the Big Bang. They looked through the Subaru Telescope's Multi-Object InfraRed Camera and Spectrograph (MOIRCS).

The researchers found that these galaxies' star content is much like that of massive galaxies shaped elliptically as seen much nearer to Earth. They also were able to identify the predecessors of the dead galaxies, finding out about the evolution of huge galaxies across 11 billion years of time in the cosmos, according to a release.

In order to learn about the length of time spent on star formation in long-dead galaxies before no more stars were formed, and about the historical record of these dead elliptical galaxies known today, the scientists looked at "fossil records," which are imprints made by stars within far-away dead galaxies, seeking clues to metal content, age and the abundance of elements. They also sought out hints to whether galaxies formed many stars in a brief period, noted the release.

Using the high-tech equipment, the team was able to look at 24 faint galaxies. They were able to create a composite spectrum from these, as a release said.

Analysis of the spectrum showed that the galaxies are already 1 billion years old, being observed 4 billion years after the Big Bang occurred. Those galaxies have 1.7 times more heavy elements than hydrogen. The researchers learned from the element readings that these galaxies' length of time for star formation was less than 1 billion years, noted the release.

The astronomers will conduct further study. The team's leader, Dr. Masato Onodera, said in the release, "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."

The study findings were published in the Astrophysical Journal.