Astronomers Discover Mature Galaxies In A Young Universe
April 30, 2014

Young Galaxy Caught Acting Like A Well-Behaved Child

redOrbit Staff & Wire Reports - Your Universe Online

With the assistance of the European Space Agency’s (ESA) Herschel Space Observatory, astronomers have located a young galaxy rotating in a calmer, more mature manner similar to more developed ones like the Milky Way.

The galaxy, which has been dubbed S0901, has apparently completed the accumulation of its gas reservoir, the ESA explained in a statement Tuesday. When galaxies form, they build mass by gravitationally attracting vast external gas clouds.

Those clouds enter haphazard orbits as they enter the galaxy, and those orbits can cause turbulence in the galaxy itself – a phenomenon that can serve as a catalyst for star formation, the agency noted. However, the study authors found that turbulence typically present in early era galaxies is not present in S0901.

The light from the galaxy, as well as that from a second identified as the Clone, has taken approximately 10 billion years to reach Earth. According to lead author James Rhoads of Arizona State University, that means the two galaxies are comparatively young at the time of observation.

“This galaxy is the equivalent of a 10-year-old. I can tell you from watching my kids' classes that 10-year-olds like to fidget! S0901 is unusual because it's not fidgeting, and instead is very well behaved,” explained Rhodes, whose study will appear in the May 20 issue of The Astrophysical Journal.

S0901 and the Clone are said to be average galaxies for their era, meaning that they are roughly 10 to 20 percent the size of the Milky Way (an average-sized galaxy by present day universe standards). They rest behind intervening groups of galaxies, and the gravity of those other galaxies warps the surrounding space.

The phenomenon has a lens-like effect that magnifies the light of the two young galaxies, and as a result of the magnification, Herschel’s Heterodyne Instrument for the Far-Infrared (HIFI) instrument could be used to study them. Rhoads and his colleagues used HIFI to detect the signature of ionized carbon, which is emitted at a wavelength of 158 micrometers and revealed the motion of the gas molecules in the two galaxies.

“This spectral line is produced in the clouds that surround star-forming regions. HIFI showed the line was broadened into a double peak, and this allowed the motion of the gas to be fitted with a model,” the ESA explained. “Firstly, the team fitted the overall rotation of the galaxy, and then the turbulence in the gas clouds.”

“To their surprise they found that galaxy S0901 was extremely well behaved. Instead of turbulence, it was found to be in orderly rotation, much more akin to the majestic galaxies of today,” the agency added. “The Clone, the second galaxy in their study, could also be fitted by an orderly rotation. However, because it was somewhat dimmer, the quality of the data was not so good. This meant that the data could also be fitted with a highly turbulent model.”

In a statement, US Herschel Project Scientist Paul Goldsmith of the NASA Jet Propulsion Laboratory (JPL) called it a “truly surprising result” that serves as a reminder that there is still much that scientists do not understand about the details of the universe’s evolution. Additional observations with other telescopes could help them figure out if there are other young galaxies that behave the same way, or if S0901 and the Clone are truly exceptional.