After using the Atacama Large Millimeter/submillimeter Array (ALMA) telescope to observe star forming regions in the Large Magellanic Cloud, a research team discovered a turbulent tug-of-war phenomenon in the 30 Doradus incubator .
The observations revealed that, despite strong stellar feedback, gravity influences the shape of the molecular cloud and, unexpectedly, promotes the formation of young massive stars.
The results of the observations were presented this week at a press conference at the 240th meeting of the American Astronomical Society (AAS, in its acronym in English), held in Pasadena (California, United States), and were published in the magazine The Astrophysical Journal (ApJ).
30 Doradus is a large stellar nursery located very close to the Milky Way (it is only 170,000 light years away), in the heart of the famous Tarantula Nebula, in the Large Magellanic Cloud. It is home to the largest cluster of stars in the cosmic neighborhood, a perfect object of observation for those who seek to study the birth and evolution of stars.
At the center of 30 Doradus is a bright stellar nursery, which has been home to more than 800,000 stars and protostars, including half a million hot, massive young stars. This region is of particular interest to those who study star formation and galaxy evolution due to the effect of gravity and stellar feedback (a phenomenon where a large amount of energy reflected back into the region by massive young stars can slow the formation of new stars), which compete to control the rate of star formation.
The new observations of 30 Doradus were made with ALMA’s extremely sensitive band 6 receivers and brought surprising news about the molecular cloud.
“Stars begin to form when dense clouds of gas become unable to resist the pull of gravity. Our new observations have revealed clear indications that gravity is shaping the thickest parts of clouds, while revealing many cloud fragments that are lower in density and too turbulent for gravity to affect them,” says Tony Wong, a professor at the University of Illinois at Urbana-Champaign and lead author of the new study.
“We thought that in the parts of the cloud closest to young massive stars we would see the clearest signs that gravity was being overcome by feedback and therefore there was less star formation. Instead of that, our observations have confirmed that even in an extremely active feedback zone, gravity is still quite strong and star formation is likely to continue,” Wong added.
“ALMA’s extraordinary resolution and sensitivity allowed us to map the entire 30 Doradus region from the southern sky,” says Mónica Rubio, a professor at the University of Chile and associate researcher at the Center for Astrophysics. and related technologies (CATA) in Chile. Magellanic Clouds and co-author of this study.
“It was a surprise to confirm that dense regions exist and survive in such a violent environment, where ultraviolet radiation and wind from hundreds of massive stars are expected to disperse and photoionize most of the gas. We are sure that the excellent conditions sky above northern Chile for millimeter wave observation and the power of ALMA will continue to amaze us with important discoveries in the years to come,” explained the Chilean scientist.
In order to get a clear idea of what’s going on in 30 Doradus, the team split the cloud into groups to see how one differs from the other. Since stars typically form in the densest parts of molecular clouds, it was very important to distinguish between denser and less dense areas in order to fully understand what is happening in 30 Doradus. This new way of proceeding made it possible to define a scheme.
“We thought interstellar gas clouds were plump or rounded structures, but it’s becoming increasingly clear that they are stretched or stringy structures,” says Tony Wong. “When we divided the cloud into sectors to measure the density differences, we saw that the densest parts do not have a random distribution, but are very well organized in these filaments. In turn, the filaments appear to be shaped by gravity, which is likely an important step in the star formation process,” the research author added.
Unlike the Milky Way, which has a relatively slow star formation rate of around seven stars (the equivalent of four solar masses) per year, the star incubators of the host galaxy of 30 Doradus, the Large Cloud of Magellan, experience real ups and downs that are often followed by frantic periods of star birth.
Thus, the team hopes that the new findings, added to future research, will shed light on the differences between the Milky Way and other more active incubator galaxies, and allow us to understand how competition between gravity and feedback affects the shape of planets. clouds. .molecules and affects the rate at which new stars form.
Remy Indebetouw, NRAO astronomer and co-author of the study, comments: “30 Doradus contains the closest massive star cluster to Earth. This type of cluster can act as a veritable pump in a galaxy, expelling gas and even altering its long-term evolution. We want to understand in detail how molecular clouds become stars: how long it takes, how quickly newly formed stars begin to affect their parent cloud, and over what distances. These are all little understood aspects at the moment. Observing these clusters will allow us to get a little closer to the answers.
According to Tony Wong, observations not only help understand the general scientific implications of star formation processes, but also reveal the history and future of galaxies.
“One of astronomy’s main mysteries is why we can still see stars forming today. What kept all the gas from collapsing into a huge fire? artifice a long time ago? What we’re discovering now can help us see what’s going on in the guts of molecular clouds and better understand how galaxies sustain star-forming processes over time.”
The research article titled The 30 Doradus molecular cloud at 0.4 parsec resolution with ALMA: physical properties and delineation of CO emitting structures, de Wong et al. (2022), published in The Astrophysical Journal. The original press release was issued by the National Radio Astronomy Observatory (NRAO) of the United States, ALMA’s partner on behalf of North America.
The Atacama Large Millimeter/submillimeter Array (ALMA), meanwhile, is an international astronomical facility, the result of a partnership between the European Southern Observatory (ESO), the National Science Foundation (NSF) of the United States and the National Institutes of Natural Sciences of Japan. (NINS) in cooperation with the Republic of Chile.
ALMA is funded by ESO on behalf of its Member States, by the NSF in cooperation with the National Research Council of Canada (NRC) and the Ministry of Science and Technology of Taiwan (MOST), and by the NINS in cooperation with Academia Sinica (AS) in Taiwan and Korea Institute of Astronomical and Space Sciences (KASI).
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