Hyper-starburst’ galaxy churns out stars, clues to universe’s evolution

Great activity of star forming is found in a recently discovered galaxy,
revealed by a group of astronomers led by University of Florida graduate student Jingzhe Ma
using NASA’s Chandra X-Ray Observatory.

The galaxy  is known as SPT 0346‐52 and it is located at 12.7 billion light years from Earth,
seen at a critical stage in the evolution of galaxies about a billion years after the Big Bang.

It was first discovered SPT 0346‐52 with the National Science Foundation’s South Pole Telescope,
then observed it with space and ground-based telescopes. Data from the NSF/ESO Atacama Large Millimeter/submillimeter Array
in Chile shows very bright infrared emission, suggesting that the galaxy is undergoing a tremendous burst of star birth.

An alternative explanation remained: Was much of the infrared emission instead caused by a swiftly growing
supermassive black hole at the galaxy’s center? Gas falling towards the black hole would become much hotter and
causing surrounding dust and gas to glow in infrared light. To explore this probability, researchers used
NASA’s Chandra X‐ray Observatory and CSIRO’s Australia Telescope Compact Array, a radio telescope.

X‐rays or radio waves were not  detected, so astronomers were able to rule out a black hole being responsible
for most of the bright infrared light.

Newborn stars

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

The forming rate of stars is  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  stark contrast to a galaxy like the
Milky Way that only forms about one solar mass of new stars per year.

“Astronomers call galaxies with lots of star formation ‘starburst’ galaxies,”
said UF astronomy professor Anthony Gonzalez, who co-lead 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 in the galaxy

means that a large reservoir of cool gas in the galaxy is being converted
into stars with unusually high effectiveness.

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,”
said co-author 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 SPT.
Its appearance is six times brighter than what it would be without gravitational lensing,
which allows astronomers to see more details than would otherwise be possible.

source: sciencedaily.com

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