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National Astronomical Observatory of Japan

ALMA telescope unveils rapid formation of new stars in distant galaxies

| Science

Galaxies forming stars at extreme rates nine billion years ago were more efficient than average galaxies today, researchers find.

A galaxy will display a burst of newly-formed stars that shine brighter than the rest. 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. A new study lead by John Silverman at the Kavli Institute for the Physics and Mathematics of the Universe, used ALMA to study carbon monoxide (CO) gas content in seven starburst galaxies far away.

The researchers found the amount of CO-emitting gas was already diminished even though the galaxy continued to form stars at high rates. These 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.

One of the galaxies forming star
Figure. (Center) Map of the galaxy PACS-867 taken by ALMA where the emission from carbon monoxide (CO) shows the molecular gas reservoir out of which stars form.
(Left) Image taken by the Hubble Space Telescope Advanced Camera for Surveys of PACS-867 that shows the rest-frame UV light from young stars in the individual components of highly disturbed galaxies as a result of a massive merger. The location of the molecular gas in Left image is overlaid (blue contours) that shows where new stars, enshrouded by dust, are forming.
(Right) Spitzer Space Telescope infrared image (3.6 micron) of PACS-867 highlights the stars embedded in dust and associated with the molecular gas.
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This research was published on October 2015 in The Astrophysical Journal Letters.

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