A group of astronomers led by University of Florida graduate student Jingzhe Ma recently discovered a galaxy that is undergoing an unusual explosion of stellar construction. The galaxy was revealed using NASA’s Chandra X-Ray Observatory.
The galaxy was named SPT 0346‐52 and it is 12.7 billion light years from Earth. It is seen about a billion years after the Big Bang. This is seen at a critical stage in the evolution of galaxies.
SPT 0346‐52 was first discovered with the National Science Foundation’s South Pole Telescope and later observed with ground and space based telescopes. Data obtained from the NSF / ESO Atacama Large Millimeter / submillimeter Array in Chile exposed very bright infrared emission. This suggests that the galaxy is undergoing a huge burst of star birth.
An alternative explanation was however also possible. It could be that much of the infrared emission is instead caused by a rapidly growing supermassive black hole at the center of the galaxy. Surrounding gas and dust would glow in infrared light when gas falling towards the black hole becomes much hotter and brighter. Researchers used CSIRO’s Australia Telescope Compact Array, a radio telescope, and NASA’s Chandra X‐ray Observatory to explore this possibility.
As radio waves or X‐rays were not detected, astronomers could rule out the possibility of a black hole causing most of the bright infrared light.
Ma is certain that this galaxy is shining brightly with the light from newborn stars and does not have a gorging black hole. This gives the team of astronomers information on how galaxies and the stars within them have evolved during some of the most primitive times in the universe.
SPT0346-52 has one of the highest rates of forming stars seen in a galaxy at about 4,500 times the mass of the Sun every year. Compared to galaxies like the Milky Way that only forms about one solar mass of new stars per year, this is indeed a massive rate.
UF astronomy professor Anthony Gonzalez, who co-authored the study, noted that galaxies with lots of star formation are called ‘starburst’ galaxies. As this term does not seem to do this galaxy justice, the team decided to call it a ‘hyper starburst’ galaxy instead
The high rate of star formation suggests that a big pool of cool gas in the galaxy is converted into stars with abnormally high efficiency. By studying more galaxies like SPT0346‐52, astronomers hope that they will learn more about the growth and formation of massive galaxies and the supermassive black holes at their cores.
Joaquin Vieira of the University of Illinois at Urbana‐Champaign and co-author of the paper says that although astronomers have known for decades that supermassive black holes and the stars in their host galaxies grow together, it is still a mystery exactly why they do this.
SPT0346-52 is interesting because although there is no evidence of a growing supermassive black hole, the team has observed an incredible burst of stars forming. Vieira would really like to study this galaxy in more detail and understand what started the star formation and how that influences the growth of a black hole.
The SPT was used to discover a population of strong gravitationally lensed galaxies of which SPT0346‐52 is only one part. Astronomers are able to see more details than would otherwise be possible due to its gravitational lensing which makes it appear about six times brighter than normal.