For Yous Data - Astronomers Probe 'Outstanding Mystery' Of How Galaxies Terminate Edifice Stars

Galaxies similar our ain Galaxy are factories that piece of job gravity to fashion novel stars out of molecular hydrogen gas.

Colour Hubble Space Telescope picture of 'self-quenching' galaxies six billion calorie-free years away. The brilliant point inwards the centre
is the compact area, too some fuzz some the edges tells researchers it's a merger remnant [Credit: KU]

"The Galaxy is turning gas into stars at virtually an average of the volume of the Sun every year," said Gregory Rudnick, professor of physics & astronomy at the University of Kansas. "The galaxy is filled amongst gas, too we're constantly getting novel gas from exterior the galaxy. This gas falls into the galaxy nether the forcefulness of gravity, gets formed into stars—and some of the gas gets blown dorsum out of the galaxy."

But some galaxies receive got stopped this procedure of star formation, too astronomers receive got been hard-pressed to explicate why.

"We come across plenty of galaxies that don't shape stars," Rudnick said. "For whatever reason, they don't receive got much gas inwards them then they can't brand novel stars. The big interrogation is why. Why exercise some galaxies nigh off? When they nigh off, they're left amongst the stars they already have, but they don't brand novel ones."

Influenza A virus subtype H5N1 fundamental to solving this puzzle may move a foreign novel bird of galaxies virtually six billion calorie-free years from basis that are inwards the procedure of violently expelling their ain gas. Now, Rudnick has teamed upward amongst scientists from some the US nether a novel grant from the National Science Foundation to written report these galaxies equally a agency to discovery out why some galaxies no longer receive got the gas necessary to shape novel stars.

Part of the procedure is to interrogation recent conventional ideas virtually the cessation of star formation.

"One of the ways people receive got come upward up amongst to nigh off star formation inwards a galaxy is to explosively take away the gas through an active galactic nucleus," Rudnick said. "Every galaxy, including our own, has a supermassive dark hole at its center. As gas falls into the dark hole, correct earlier it hits the dark hole, it gets super-hot, too the unloosen energy it gives off tin truly blow out the residual of the gas from the galaxy. People similar this take in because it's a machinery that's energetic plenty to exercise the project of expelling all the gas from the galaxy."

However, inwards 2007 a squad of astronomers discovered a laid of "self-quenching" galaxies that receive got nigh downward star formation yesteryear some other mechanism. Rudnick after joined this team, which has led a multiyear investigation of these objects.

CO J(2 → 1) maps of the galaxy SDSS J1341?0321 averaged over 333 km s-1channels spanning ΔV = ± 1500 km s-1
(labels plough over channel centers) relative to the systemic redshift. Contours showtime at 2σ too are logarithmically spaced
at 0.2 dex multiples of σ. Dashed contours are negative equivalents. The crosshair indicates the peak
of the stellar emission inwards the HST/F814W imaging. Black ellipses exhibit the fwhm
of the synthesized beam [Credit: KU]

"Our enquiry has constitute this variety of galaxy that has gas existence blown out of it at thousands of kilometers per second—that's over 3,500 times faster than a jet plane—but there's absolutely no evidence of whatsoever variety of gas falling into a dark hole," the KU researcher said. "So, there's a interrogation of whether or non that black-hole procedure is required or if in that location are other ways of doing it. You realize, 'Wait a minute, the universe isn't that simple.' This could say us truly novel too cool things virtually how galaxies evolve."

With improve images of the galaxies from the Hubble Space Telescope, Rudnick too his collaborators realized gas could move expelled from the galaxies purely yesteryear the concentrated calorie-free of the stars inwards the galaxies, amongst no demand for whatsoever extra unloosen energy from gas falling onto the dark hole.

"Using HST, these fuzzy dots nosotros saw earlier from our telescopes on the basis at i time showed these features that looked similar a collision of galaxies—they had lots of streams of stars around. Most surprisingly, they were incredibly compact," Rudnick said. "The Galaxy has all its stars too gas spread out over 100,000 calorie-free years, pregnant it takes calorie-free 100,000 years to larn from i side to another. These galaxies, which are equally massive equally the Milky Way, await similar they had most of their volume crammed into something similar 1,000 calorie-free years. So, they're massive, but they're equally good super-concentrated. The take in nosotros started developing is that mayhap these galaxies are then compact that all the starlight from all the stars inwards these galaxies jammed into this minor infinite is intense plenty yesteryear itself to drive the gas out of the galaxies."

Rudnick said the take in is that stars emit calorie-free particles that would bump into particles of gas too "give them a niggling push. The amount of many of these niggling pushes is plenty to force all the gas out of the galaxy at incredible speeds."

"When you lot condense an entire Galaxy into a minor spot because of a merger of galaxies, it tin drive hundreds of billions of stars to move inwards a really compact place," he said. "When that happens, you lot tin pose plenty calorie-free into a minor plenty space, too that tin move plenty to force all of the gas out of a galaxy, amongst no extra unloosen energy needed from gas falling into a supermassive dark hole."

The NSF grant piece of job volition enable farther observation too written report of this bird of self-quenching galaxies. Rudnick said he too his colleagues volition move studying the galaxies inwards equally many ways equally possible, using telescopes such equally NASA's CHANDRA X-ray Observatory, the Keck Observatories inwards Hawaii too the Atacama Large Millimeter Array (ALMA) inwards Chile.

"How mutual is it that these galaxies are shutting themselves off this way?" he asked. "Is the galaxy truly able to blow out all its gas completely—or are nosotros seeing truly fast, minor stream? It's similar you lot receive got a teakettle on the stove too it's hot too a current of gas is shooting out of the teakettle. You know this gas is shooting out, too we'd similar to know if there's plenty gas shooting out that it volition empty the teakettle completely."

Rudnick has but co-authored a newspaper appearing inwards Astrophysical Journal that used the ALMA telescope to await inside a self-quenching galaxy at "the densest, coldest gas—the materials that's truly forming the stars." In that paper, they ask, "What evidence exercise nosotros receive got for that gas blowing out?"

The KU researcher too his co-authors constitute the galaxy to move the compact remains of a trigger-happy merger betwixt ii galaxies. This "merger remnant" equally good hosts huge winds of dense molecular gas but without whatsoever delineate of an active galactic nucleus. They wanted to create upward one's heed how the fast the dense gas was gas existence driven out of the galaxy.

"ALMA uses calorie-free amongst much a longer wavelength than visible light—with a wavelength of a 10th of a millimeter," Rudnick said. "It turns out carbon monoxide molecules inwards this gas plough over off calorie-free you lot tin come across amongst a telescope from Earth. Most of the gas is truly hydrogen, but hydrogen is difficult to come across from Earth, then nosotros selection a delineate gas. It's a lot similar natural gas, you lot can't olfactory holding it, then they pose something inwards it to arrive olfactory holding similar rotten eggs. Carbon monoxide industrial plant similar that, inwards that it tells us where the hard-to-see molecular hydrogen is. We piece of job ALMA to discovery carbon monoxide too piece of job that to discovery how much total molecular gas. We constitute this gas, which makes upward much of what the galaxy has, is moving from the centre of the galaxy at 1,000 kilometers per second. It's truly the materials that forms stars that's existence blown out."

Source: University of Kansas [September 12, 2018]


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