While observing a newly-dormant galaxy using the Atacama Large Millimeter/submillimeter Array (ALMA) and the Hubble Space Telescope (HST), scientists discovered that it had stopped forming stars not because it had used up all of its gas but because most of its star-forming fuel had been thrown out of the system as it merged with another galaxy. The result is a first for ALMA scientists. What's more, if proven common, the results could change the way scientists think about galaxy mergers and deaths. The results of the research are published in The Astrophysical Journal Letters.

As galaxies move through the Universe, they sometimes encounter other galaxies. As they interact, each galaxy's gravity pulls on the other. The ensuing tug-of-war flings gas and stars away from the galaxies, leaving behind streams of material known as tidal tails.

And that's just what scientists believe happened to SDSS J1448+1010, but with a plot twist. The massive galaxy, which was born when the Universe was about half its current age, has nearly completed merging with another galaxy.

During observations with the HST and ALMA- an international collaboration in which the U.S. National Science Foundation's National Radio Astronomy Observatory (NRAO) is a partner- scientists discovered tidal tails containing roughly half of the entire system's cold, star-forming gas. The discovery of the forcefully discarded material- equal to 10 billion times the mass of Earth's Sun- was an indication that the merger may be responsible for snuffing out star formation, and that's something scientists didn't expect.

"What initially made this massive galaxy interesting was that, for some reason, it suddenly stopped forming stars about 70 million years ago immediately following a burst of star-forming activity.

Most galaxies are happy to just keep forming stars," said Justin Spilker, an astronomer at Texas A and M University and the lead author of the paper. "Our observations with ALMA and Hubble proved that the real reason the galaxy stopped forming stars is that the merger process ejected about half the gas fuel for star formation into intergalactic space. With no fuel, the galaxy couldn't keep forming stars."

The discovery is shedding light on the processes by which galaxies live or die, and helping scientists to better understand their evolution.

"When we look out at the Universe, we see some galaxies that are actively forming new stars, like our own Milky Way, and some that aren't. But those 'dead' galaxies have many old stars in them, so they must have formed all of those stars at some point and then stopped making new ones," said Wren Suess, a cosmology fellow at the University of California Santa Cruz and a co-author of the paper.

"We still don't yet understand all of the processes that make galaxies stop forming stars, but this discovery shows just how powerful these major galaxy mergers are, and how much they can affect how a galaxy grows and changes over time."

Because the new result is from a single observation, it is currently unclear just how common this tug-of-war and its resultant quiescence may be. However, the discovery challenges long-held theories about exactly how star formation stops and galaxies die and has provided scientists with an exciting new challenge: to find more examples.

"While it's pretty clear from this system that cold gas really can end up way outside of a merger system that shuts off a galaxy, the sample size of one galaxy tells us very little about how common this process is," said David Setton, a graduate student in the department of physics and astronomy at the University of Pittsburgh and a co-author of the paper.

"But, there are many galaxies out there like J1448+1010 that we're able to catch right in the middle of those crashes and study exactly what happens to them when they go through that stage. The ejection of cold gas is an exciting new piece of the quiescence puzzle, and we're excited to try to find more examples of this."

Spilker added, "Astronomers used to think that the only way to make galaxies stop forming stars was through really violent, fast processes, like a bunch of supernovae exploding in the galaxy to blow most of the gas out of the galaxy and heat up the rest. Our new observations show that it doesn't take a 'flashy' process to cut off star formation. The much slower merging process can also put an end to star formation and galaxies."

Star formation suppression by tidal removal of cold molecular gas from an intermediate-redshift massive post-starburst Research Report:galaxy

Related Links
National Radio Astronomy Observatory
Stellar Chemistry, The Universe And All Within It

Tweet

Thanks for being here; We need your help. The SpaceDaily news network continues to grow but revenues have never been harder to maintain. With the rise of Ad Blockers, and Facebook - our traditional revenue sources via quality network advertising continues to decline. And unlike so many other news sites, we don't have a paywall - with those annoying usernames and passwords. Our news coverage takes time and effort to publish 365 days a year. If you find our news sites informative and useful then please consider becoming a regular supporter or for now make a one off contribution.
SpaceDaily Contributor $5 Billed Once credit card or paypal		SpaceDaily Monthly Supporter $5 Billed Monthly paypal only

Red Giant Betelgeuse was yellow some 2,000 years ago
Jena, Germany (SPX) Sep 06, 2022
With progressing nuclear fusion in the center of a star, brightness, size, and color also change. Astrophysicists can derive from such properties important information on age and mass of a star. Those stars with significantly more mass than our Sun are blue-white or red - the transition from red via yellow and orange is relative rapid for astronomical time-scales. Astrophysicists of Friedrich Schiller University Jena, Germany, together with colleagues of other subjects from the USA and Italy, have ... read more