Galaxies Were More Efficient When The Universe Was Young

Thanks to powerful space telescopes, scientists have captured the carbon monoxide emissions of starbursts in the early universe.

AsianScientist (Oct. 23, 2015) – Galaxies forming stars at extreme rates nine billion years ago were more efficient than average galaxies today, according to a study published in Astrophysical Journal Letters.

The majority of stars have been believed to lie on a ‘main sequence,’ where the larger a galaxy’s mass, the higher its efficiency to form new stars. However, every now and then a galaxy will display a burst of newly-formed stars that shine brighter than the rest. A collision between two large galaxies is usually the cause of such starburst phases, where the cold gas residing in the giant molecular clouds becomes the fuel for sustaining such high rates of star formation.

The question astronomers have been asking is whether such starbursts in the early universe were the result of having an overabundant gas supply, or whether galaxies converted gas more efficiently.

To address this question, a team of researchers led by Professor John Silverman of Kavli Institute studied the carbon monoxide gas content in seven starburst galaxies far away from when the Universe was a young four billion years old. They reported that the amount of CO-emitting gas was already diminished even though the galaxy continued to form stars at high rates.

This observation was made feasible by the advent of Atacama Large Millimeter Array (ALMA), located on a mountaintop plateau in Chile, which works in tandem to detect electromagnetic waves at a wavelength range in the millimeter (pivotal for studying molecular gas) and a sensitivity level that is just starting to be explored by astronomers today.

The researcher’s observations are similar to those recorded for starburst galaxies near Earth today, but the amount of gas depletion was not quite as rapid as expected. This led researchers to conclude there might be a continuous increase in the efficiency depending on how high above the rate of forming stars is from the main sequence.

This study relied on a variety of powerful telescopes available through the COSMOS survey. Only the Spitzer and Herschel Observatories could measure accurate rates of star formation, and the Subaru Telescope could confirm the nature and distance of these extreme galaxies using spectroscopy.

“These observations clearly demonstrate ALMA’s unique capability to measure with ease a critical component of high redshift galaxies thus indicative of the remarkable results to come from ALMA,” commented Silverman.

The article can be found at: Silverman et al. (2015) A Higher Efficiency of Converting Gas to Stars Pushes Galaxies at z ~ 1.6 Well Above the Star-Forming Main Sequence.

———

Source: Kavli Institute for the Physics and Mathematics of the Universe; Photo: NASA.
Disclaimer: This article does not necessarily reflect the views of AsianScientist or its staff.

Asian Scientist Magazine is an award-winning science and technology magazine that highlights R&D news stories from Asia to a global audience. The magazine is published by Singapore-headquartered Wildtype Media Group.

Related Stories from Asian Scientist