Massive Galaxies Are Much Older than First Thought

A recent study has demonstrated that massive galaxies, structures larger even than the Milky Way is now, existed very early on in the history of the Universe, perhaps as little as 1.5 to 2 billion years after the Big Bang.

According to the research, these galaxies may have been 5 to 10 times more massive than our own. This is very interesting, because the Milky Way now has a diameter of 100,000 light-years, and tips the scales at 100 billion solar masses.

It contains between 100 and 400 billion stars, depending on the methods and computer models used to carry out the calculations. But the galaxy needed several billions of years to grow to such proportions.

The new investigation is basically suggesting that it's possible galaxies a lot larger than formed in the early Universe in just a fraction of the time the Milky Way needed. The findings were made by an international consortium led by experts at the Tufts University.

The researchers found galaxies with redshifts between 3 and 4, which means that they existed when the Cosmos was less than 2 billion years old. “We have found a relatively large number of very massive, highly luminous galaxies that existed almost 12 billion years ago,” says Danilo Marchesini.

“These results appear to disagree with the latest predictions from models of galaxy formation and evolution,” adds the expert, who is an assistant professor of physics and astronomy at the Tufts School of Arts and Sciences.

He is also the lead author of the new research effort. “Current understanding of the physical processes responsible in forming such massive galaxies has difficulty reproducing these observations,” he says.

Astronomers from the Yale University, the Carnegie Observatories, the Leiden University, the Princeton University, the University of Kansas and the University of California in Santa Cruz (UCSC) were also involved in the new study, Daily Galaxy reports.

Interestingly, it was found that more than 80 percent of these early galaxies exhibited tremendous luminosity in infrared wavelengths. The experts believe that this may have two explanations.

The first is that stellar nurseries in these galaxies produce a few thousand solar masses in new stars per year. These levels are hundreds of times greater than determined possible via spectral energy distribution (SED) modeling.

The second explanation is that the cosmic structures contain active galactic nuclei (AGN), which are being powered by supermassive black holes. How the dark behemoths may have developed in such a short time is still unclear thought.

“Either way, it is clear that our understanding of how massive galaxies form is still far from satisfactory,” Marchesini says.

“The existence of these galaxies so early in the history of the Universe, as well as their properties, can provide very important clues on how galaxies formed and evolved shortly after the Big Bang,” he concludes.