Thursday, April 28, 2022 05:44 PM
It was previously thought that post-starburst galaxies scatter all their gas and dust, the fuel needed to form new stars, in violent bursts of energy and at an unusual speed.
And new data, from ALMA, or the Atacama Large Millimeter/ Sub-millimeter Array, now reveals that these galaxies don’t scatter all their star-formed fuel after all. Instead, after their supposed end, these dormant galaxies hold and compress large amounts of highly concentrated, turbulent gas. But contrary to expectations, it does not use it to form stars.
In most galaxies, scientists expect the gas to be distributed in a similar way to starlight. But for post-starburst galaxies, or PSBs, this is not the case.
Post-starburst galaxies differ from other galaxies in that they were born in the aftermath of violent collisions or mergers between galaxies.
Galactic mergers usually lead to massive bursts of star formation, but in post-stellar galaxies this explosion slows down and almost stops once it begins.
As a result, scientists previously thought that there was little left of star-forming fuel left in the central star-forming factories of these galaxies.
Until now, the prevailing belief was that molecular gases were redistributed to radii far beyond galaxies, either through stellar processes or through the effects of black holes.
The new findings challenge this theory
“We’ve known for some time that large amounts of molecular gas are still present near post-starburst galaxies but we haven’t been able to pinpoint where it is, which in turn has prevented us from understanding why it stopped,” said Adam Smersina, an astronomer at the University of Washington and the lead author on the study. These galaxies are about star formation. Now, we have discovered a large amount of gas left inside galaxies and that the remaining gas is very compressed. Although this compressed gas should be stars efficiently, it is not. In fact, it is less than 10% efficiency similarly expected to be compressed gas.
In addition to being compact enough to form stars, the gas in the observed inactive — or quiet — galaxies had another surprise in store for the team: It was often, if not always, centrally located, and surprisingly turbulent. Together, these two characteristics raise more questions than answers for scientists.
“The rates of star formation in the post-starburst galaxies we have observed are much lower than in other galaxies, although there appears to be a lot of fuel to sustain this process,” Smyrsina said. “In this case, star formation may be suppressed by turbulence.” In gas, just like strong winds can put out fire.However, star formation can also be enhanced by turbulence, just like winds can increase flames, so generating this turbulent energy, and exactly how it contributes to the stillness, is a remaining question in this work”.
Decker French, an astronomer at the University of Illinois and co-author of the study added: “These findings raise the question of what energy sources exist in these galaxies to cause turbulence and prevent gas from forming new stars. One possibility is energy from the accretion disk of central supermassive black holes in these galaxies. Galaxies”.
A clear understanding of the processes that govern the formation of stars and galaxies is key to providing an understanding of the universe and our place in it. The discovery of turbulent, compressed gas in inactive galaxies gives researchers further clues to the puzzle of how galaxies in particular live, evolve and die over billions of years. This means additional research in the future with the help of Alma, which sees the “unseen” starkly.
Source: Science Daily
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