An international team of astronomers has detected one of the highest rates of star formation ever seen, in the gravitational lensing galaxy SPT0346-52, 12.7 billion light-years from Earth.
Using the “ALMA” telescope (Atacama Large Millimeter/submillimeter Array), a modern telescope located in the Atacama Desert in the Andes mountains north of Chile, scientists were able to observe a critical stage in the evolution of galaxies, regarding a billion years following the Big Bang.
The data collected might be essential in improving our knowledge regarding the galaxy SPT0346-52 (also referred to as SPT-S J034640-5204.9), and other similar star formation systems.
The interstellar medium (ISM) is the matter and radiation found in the interstellar space in the galaxy. However, the interstellar medium in distant galaxies is difficult to study directly due to cosmic dimming and angular resolution limitations.
So a group of scientists, led by Katrina C. Leetke of the Steward Observatory in Tucson, Arizona, used the ALMA telescope to investigate the interstellar medium in the high redshift galaxy SPT0346-52.
The ALMA telescope is an excellent tool for such observations because it offers new opportunities to explore the physical conditions in early galaxies through the emission of far-infrared rays at rest.
Discovered in 2010 by Dr. Joaquín Vieira of the University of Illinois and colleagues using the National Science Foundation’s South Pole Telescope, SPT 0346-52 is a galaxy that forms dusty stars with gravitational lensing (DSFG) at a redshift of approximately 5.66. (Redshift is the phenomenon of increasing the length of the electromagnetic wave coming to us from a celestial body as a result of its speed away from us).
It has a visible far-infrared luminosity at the level of 110 trillion solar luminosity, and an intrinsic star formation rate of regarding 4,200 solar masses/year/kpc2, making it the most intensely star-forming galaxy discovered by the South Pole Telescope survey.
The galaxy was then observed using the European Space Agency’s Hubble, Spitzer and ESA space observatories, the ALMA array and the European Space Agency’s Very Large Telescope.
Dr. Vieira and co-authors were intrigued by SPT0346-52 when ALMA data revealed a very bright infrared emission from this galaxy. This indicates that the galaxy is witnessing a huge explosion in the birth of stars.
However, another possible explanation for the increased infrared emissions is the presence of a rapidly growing supermassive black hole in the galactic center.
In this scenario, the gas falling into the black hole would become hotter and brighter, causing the surrounding dust and gas to glow in infrared light.
To distinguish between these two possibilities, astronomers used the Chandra and ATCA telescopes. Neither X-rays nor radio waves were detected, so they were able to rule out the presence of a growing black hole that generates most of the bright infrared light.
“This gives us information regarding how galaxies and the stars within them evolved during some of the earliest times in the universe,” said team member Jinjai Ma, a graduate student at the University of Florida and first author of the study, which was published in the arXiv.org preprint.
At SPT0346-52, stars are forming at a rate of 4,500 times the mass of the Sun each year, one of the highest rates seen in the galaxy. This is in contrast to a galaxy like our Milky Way, which only forms one solar mass of new stars each year.
Team member Professor Anthony Gonzalez, from the University of Florida, explained: “Astronomers call galaxies with a lot of starburst galaxies. The term doesn’t seem to do galactic justice, so we call it a superstarburst galaxy.”
The high rate of star formation indicates that a large reservoir of cold gas at SPT 0346-52 is being transformed into extraordinarily efficient stars.
