Cosmic cartographers map nearby Universe revealing the diversity of star-forming galaxies
A team of astronomers using the Atacama Large Millimeter/submillimeter Array (ALMA) has completed the first census of molecular clouds in the nearby universe, revealing that contrary to previous scientific opinion, these stellar nurseries do not all look and act the same. In fact, they're as diverse as the people, homes, neighborhoods and regions that make up our own world.
Stars are formed out of clouds of dust and gas called molecular clouds, or stellar nurseries. Each stellar nursery in the universe can form thousands or even tens of thousands of new stars during its lifetime. Between 2013 and 2019, astronomers on the PHANGS project (Physics at High Angular Resolution in Nearby GalaxieS) conducted the first systematic survey of 100,000 stellar nurseries across 90 galaxies in the nearby universe to get a better understanding of how they connect back to their parent galaxies.
"We used to think that all stellar nurseries across every galaxy must look more or less the same, but this survey has revealed that this is not the case, and stellar nurseries change from place to place," said Adam Leroy, associate professor of astronomy at Ohio State University (OSU), and lead author of the paper presenting the PHANGS ALMA survey. "This is the first time that we have ever taken millimeter-wave images of many nearby galaxies that have the same sharpness and quality as optical pictures. And while optical pictures show us light from stars, these ground-breaking new images show us the molecular clouds that form those stars."
"To understand how stars form, we need to link the birth of a single star back to its place in the universe. It's like linking a person to their home, neighborhood, city and region. If a galaxy represents a city, then the neighborhood is the spiral arm, the house the star-forming unit, and nearby galaxies are neighboring cities in the region," said Eva Schinnerer, an astronomer at the Max Planck Institute for Astronomy (MPIA) and principal investigator for the PHANGS collaboration "These observations have taught us that the 'neighborhood' has small but pronounced effects on where and how many stars are born."
To better understand star formation in different types of galaxies, the team observed similarities and differences in the molecular gas properties and star formation processes of galaxy disks, stellar bars, spiral arms, and galaxy centers. They confirmed that the location, or neighborhood, plays a critical role in star formation.
"By mapping different types of galaxies and the diverse range of environments that exist within galaxies, we are tracing the whole range of conditions under which star-forming clouds of gas live in the present-day universe. This allows us to measure the impact that many variables have on the way star formation happens," said Guillermo Blanc, an astronomer at the Carnegie Institution for Science, and a co-author on the paper.
"How stars form, and how their galaxy affects that process, are fundamental aspects of astrophysics," said Joseph Pesce, National Science Foundation's program officer for NRAO/ALMA. "The PHANGS project utilizes the exquisite observational power of the ALMA observatory and has provided remarkable insight into the story of star formation in a new and different way." [Entire article here.]
