The study of nearby galaxies gives new information on the formation of stars.

Astronomers have taken a big step forward in understanding the dark and violent places where stars are born.

In the past five years, an international team of researchers has conducted the first systematic investigation of “stellar nurseries” in our part of the universe, mapping the more than 100,000 such nurseries in more than 90 nearby galaxies and providing information. new information on the origins of stars.

“Every star in the sky, including our own sun, was born in one of these star nurseries,” said Adam Leroy, associate professor of astronomy at Ohio State University and one of the project’s leaders. .

“These nurseries are responsible for the construction of galaxies and planets, and they are only a vital part of the story of our coming here. But this is truly the first time that we have had a full view of these stellar nurseries across the entire neighboring universe. “

The project is called PHANGS-ALMA, and the research was made possible by the ALMA telescope array located in the Andes mountains in Chile.

ALMA, the world’s most powerful radio telescope, is an international facility with strong American participation led by the National Science Foundation and the National Radio Astronomy Observatory.

The power of this facility allowed the team to study stellar nurseries in a diverse set of 90 galaxies, whereas previous studies had primarily focused on an individual galaxy or part of a galaxy.

“When optical telescopes take pictures, they pick up starlight. When ALMA takes a photo, she sees the glow of gas and dust that will form stars, ”said Jiayi Sun, an Ohio State doctoral student who is completing a thesis based on the survey this month.

“The novelty of PHANGS-ALMA is that we can use ALMA to take pictures of many galaxies, and these images are as sharp and detailed as those taken by optical telescopes. It just wasn’t possible before.

The investigation more than increased the amount of data on stellar nurseries more than tenfold, Leroy said. This has given astronomers a much more precise perspective of what these nurseries look like across our corner of the universe.

Based on these measurements, they discovered that stellar nurseries are surprisingly diverse across galaxies, only live relatively a short time in astronomical terms, and are not very efficient at making stars.

The diversity of these stellar nurseries was a surprise.

“For a long time, the conventional wisdom among astronomers was that all stellar nurseries looked more or less alike,” Sun said.

“But with this investigation, we can see that it really isn’t. While there are some similarities, the nature and appearance of these nurseries change within and between galaxies, just as cities or trees can vary significantly as you move from place to place. other across the world.

For example, nurseries in large galaxies and those in the center of galaxies tend to be denser and more massive, and much more turbulent, he said. Star formation is much more violent in these clouds, the results suggest.

“So the properties of these nurseries and even their ability to create stars seem to depend on the galaxies they live in,” Sun said.

The results of the survey also showed that these stellar nurseries only live 10 to 30 million years, which is a relatively short period in astronomical terms. And the team used the same metrics to assess how efficiently these stellar nurseries turned their gas and dust into stars – and they turned out not to be that effective.

“This survey allows us to paint a much more complete picture of the life cycle of these regions, and we find that they are short-lived and inefficient,” Leroy said.

“It is not chance that destroys these nurseries, but the new stars they make. They are very ungrateful children.

The radiation and heat coming out of these young stars begin to disperse and dissolve the clouds, eventually destroying them before they can convert most of their mass.

After more than five years of observations, the survey was recently completed and summarized by the PHANGS-ALMA team in two recent papers accepted at Astrophysical Journal Supplements Series.

The publication of these two new articles marks an important milestone and the data collected by the project team is now publicly available. Researchers have already used PHANGS-ALMA to produce more than 20 scientific publications. Ten papers detailing the results of the PHANGS survey were recently presented to the 238th meeting of the American Astronomical Society.

“We have an incredible data set here that will continue to be useful,” Leroy said. “This is truly a new vision for galaxies and we expect to learn from it for years to come.”

To learn more about this research, read Map of the nearby universe created by cosmic cartographers reveals the diversity of star-forming galaxies.

Reference: “PHANGS-ALMA: Arcsecond CO (2-1) Imaging of Nearby Star-Forming Galaxies” by Adam K. Leroy, Eva Schinnerer, Annie Hughes, Erik Rosolowsky, Jérôme Pety, Andreas Schruba, Antonio Usero, Guillermo A. Blanc , Mélanie Chevance, Eric Emsellem, Christopher M. Faesi, Cinthya N. Herrera, Daizhong Liu, Sharon E. Meidt, Miguel Querejeta, Toshiki Saito, Karin M. Sandstrom, Jiayi Sun, Thomas G. Williams, Gagandeep S. Anand, Ashley T. Barnes, Erica A. Behrens, Francesco Belfiore, Samantha M. Benincasa, Ivana Bešlić, Frank Bigiel, Alberto D. Bolatto, Jakob S. den Brok, Yixian Cao, Rupali Chandar, Jérémy Chastenet, I-Da Chiang, Enrico Congiu , Daniel A. Dale, Sinan Deger, Cosima Eibensteiner, Oleg V. Egorov, Axel García-Rodríguez, Simon CO Glover, Kathryn Grasha, Jonathan D. Henshaw, I-Ting Ho, Amanda A. Kepley, Jaeyeon Kim, Ralf S. Klessen, Kathryn Kreckel, Eric W. Koch, JM Diederik Kruijssen, Kirsten L. Larson, Janice C. Lee, Laura A. Lopez, Josh Machado, Ness Mayker, Rebecca McElroy, Eric J Murphy, Eve C. Ostriker, Hsi-An Pan, Ismael Pessa, Johannes Puschnig, Alessandro Razza, Patricia Sánchez-Blázquez, Francesco Santoro, Amy Sardone, Fabian Scheuermann, Kazimierz Sliwa, Mattia C. Sormani, Sophia K. Stuber, David A. Thilker, Jordan A. Turner, Dyas Utomo, Elizabeth J. Watkins, Bradley Whitmore, Accepted, Supplement to the Journal of Astrophysics.
arXiv: 2104.07739