This graphic shows a frame from a computer simulation of a burst of star formation following a galactic merger. (Credit: Simons Fdn./Moore Fdn./Flatiron Inst./Caltech/C. Hayward & P. Hopkins)

galaxies

Telescopes spot galaxy bursting with new stars

A galaxy 12.7 billion light years from Earth is undergoing a tremendous burst of star birth.

Astronomers studied the galaxy known as SPT 0346-52 with space- and ground-based telescopes and recorded extremely bright infrared emission.

They used NASA’s Chandra X-Ray Observatory to rule out the possibility that the emissions were caused by a rapidly growing supermassive black hole at the galaxy’s center.

“We now know that this galaxy doesn’t have a gorging black hole, but instead is shining brightly with the light from newborn stars,” says Jingzhe Ma, a University of Florida graduate student who led the project. “This gives us information about how galaxies and the stars within them evolve during some of the earliest times in the universe.”

Stars are forming at a rate of about 4,500 times the mass of the sun every year in SPT0346-52, one of the highest rates seen in a galaxy. This is in contrast to a galaxy like the Milky Way that only forms about one solar mass of new stars per year.

composite image of SPT 0346-52
The absence of X-rays from Chandra shows that there is no actively growing, supermassive black hole in the center of the galaxy. This means that the rate amount of infrared emission detected by other telescopes can only be explained by an extremely high rate of star formation. (Credit: X-ray: NASA/CXC/Univ of Florida/J.Ma et al; Optical: NASA/STScI; Infrared: NASA/JPL-Caltech; Radio: ESO/NAOJ/NRAO/ALMA)

“Astronomers call galaxies with lots of star formation ‘starburst’ galaxies,” says astronomy professor Anthony Gonzalez, a coauthor of the study. “That term doesn’t seem to do this galaxy justice, so we are calling it a ‘hyper-starburst’ galaxy.”

The high rate of star formation implies that a large reservoir of cool gas in the galaxy is being converted into stars with unusually high efficiency.

Gravitational lensing reveals faintest galaxy yet

Astronomers hope that by studying more galaxies like SPT0346-52 they will learn more about the formation and growth of massive galaxies and the supermassive black holes at their centers.

“For decades, astronomers have known that supermassive black holes and the stars in their host galaxies grow together,” says coauthor Joaquin Vieira of the University of Illinois at Urbana-Champaign. “Exactly why they do this is still a mystery.

“SPT0346-52 is interesting because we have observed an incredible burst of stars forming, and yet found no evidence for a growing supermassive black hole. We would really like to study this galaxy in greater detail and understand what triggered the star formation and how that affects the growth of the black hole.”

SPT0346-52 is part of a population of strong gravitationally lensed galaxies discovered with the National Science Foundation’s South Pole Telescope. It appears about six times brighter than it would without gravitational lensing, which enables astronomers to see more details than would otherwise be possible.

A paper describing the results appears in the Astrophysical Journal.

Source: University of Florida

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