Scientists are now learning how massive elliptical galaxies originated and why they stopped creating new stars earlier compared to the other galaxies in the universe.
Dubbed as red and dead galaxies, elliptical-shaped galaxies are those which have burned out as early as when the universe was 3 billion years old. These galaxies are predominantly red in color, compared to star-making galaxies which are mostly blue. However, elliptical galaxies have the same mass as other spiral galaxies, but their stars were crammed in an area three times smaller than star-making galaxies.
Astrophysics and cosmology professor from the Niels Bohr Institute in Copenhagen, SuneToft, explained to SPACE.com, "This means that the density of stars was 10 times greater. Furthermore, the galaxies were already dead, so they were no longer forming new stars. It was a great mystery"
To study more about these elliptical galaxies, the researchers collected data from ground-based and space-based telescopes, including NASA's Hubble Space Telescope and the Cosmic Assembly Near-Infrared Deep Extragalactic Legacy Survey (CANDELS). The latter is primarily designed to explore the evolution of galaxies as early as 1 billion years after the Big Bang by capturing photos of from up to 250, 000 galaxies.
Toft found out that these galaxies burned out early because they quickly consumed all the gas available to them. The galaxies started out as intense starbursts, and during their first 1 to 2 billion years, they have been rapidly producing stars. These galaxies proceeded into merging with other galaxies, allowing them to assume their giant elliptical shape.
"We at last show how these compact galaxies can form, how it happened, and when it happened," Toft said to SPACE.com. "This basically is the missing piece in the understanding of how the most massive galaxies formed, and how they evolved into the giant ellipticals of today."
