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ALMA Spots Circumstellar Disk around Young Star in Large Magellanic Cloud

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Astronomers using the Atacama Large Millimeter/submillimeter Array (ALMA) have detected a rotating gaseous structure around an extragalactic massive young stellar object in the star-forming region N180, which is part of the Large Magellanic Cloud, a neighboring dwarf galaxy, 163,000 light-years away. They’ve observed motions in gas around the star consistent with a so-called Keplerian accretion disk — the kind that feeds the growth of stars through infalling material. This is the most distant disk around a massive star ever to be directly detected.

Left: this image from the Multi Unit Spectroscopic Explorer (MUSE) on ESO’s Very Large Telescope shows the parent cloud LHA 120-N 180B in which the HH 1177 system was first observed. Center: this image shows the jets that accompany HH 1177; the top part of the jet is aimed slightly towards us and thus blueshifted; the bottom one is receding from us and thus redshifted. Right: this image from ALMA shows the rotating disk around the star, similarly with sides moving towards and away from us. Image credit: ESO / ALMA / NAOJ / NRAO / McLeod et al.

“The Large Magellanic Cloud is a convenient environment for searching for the extragalactic counterparts of the accreting massive young stellar objects known in the Milky Way,” said Durham University astronomer Anna McLeod and her colleagues.

“For example, there is the recent detection of molecular outflows, as well as the discovery of Herbig-Haro object 1177 (HH 1177), a collimated bipolar jet driven by a massive young stellar object.”

“Although the detection of a molecular outflow from a forming star does not necessarily imply the presence of an accretion disk, collimated jets are generally taken as clear signposts for ongoing disk accretion.”

“To date, there has been no direct detection of a rotating circumstellar Keplerian disk or toroid in an external galaxy, making the HH 1177 star/jet system an ideal target to search for these.”

“ALMA now enables the high-sensitivity and high-angular-resolution observations needed to detect and resolve rotating circumstellar gas in extragalactic massive young stellar objects.”

The rotating disk detected by ALMA is feeding the central star of the HH 1177 system.

“When I first saw evidence for a rotating structure in the ALMA data, I could not believe that we had detected the first extragalactic accretion disk; it was a special moment,” Dr. McLeod said.

“We know disks are vital to forming stars and planets in our Galaxy, and here, for the first time, we’re seeing direct evidence for this in another galaxy.”

“We are in an era of rapid technological advancement when it comes to astronomical facilities.”

“Being able to study how stars form at such incredible distances and in a different galaxy is very exciting.”

“Massive stars, like in the HH 1177 system, form much more quickly and live far shorter lives than low-mass stars like our Sun.”

“In our Galaxy, these massive stars are notoriously challenging to observe and are often obscured from view by the dusty material from which they form at the time a disk is shaping around them.”

“Unlike similar circumstellar disks in the Milky Way, this system is optically visible, likely due to the lower dust and metal content of its surrounding environment.”

“This gives us a peek into the dynamics of accretion that are typically hidden behind veils of gas and dust.”

The analysis of the disk suggests an inner Keplerian region transitioning to infalling material at larger distances from the central star of HH 1177. The star is estimated to be around 15 times the mass of our Sun.

“While bearing many familiar characteristics of Milky Way disks, some intriguing differences also emerge,” the astronomers said.

“The low metal content typical of the Large Magellanic Cloud seems to make the disk more stable against fragmentation.”

“The successful detection of this extragalactic circumstellar disk boosts prospects for finding more such systems with ALMA and the upcoming Next Generation Very Large Array (ngVLA).”

“Studying star and disk formation across different galactic environments will help complete our understanding of stellar origins.”

“We are in an era of rapid technological advancement when it comes to astronomical facilities,” Dr. McLeod said.

“Being able to study how stars form at such incredible distances and in a different galaxy is very exciting.”

The discovery is described in a paper published today in the journal Nature.

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A.F. McLeod et al. A probable Keplerian disk feeding an optically revealed massive young star. Nature, published online August 29, 2023; doi: 10.1038/s41586-023-06790-2

Source : Breaking Science News

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