The birth of stars in colliding galaxies
Contrary to what one might think, the collision between galaxies does not cause the destruction of stars, but rather creates ideal conditions for the birth of millions of new stars. A recent study, conducted by a team of researchers at Penn State University and taking advantage of the potential of NASA’s Hubble Space Telescope, has highlighted this surprising phenomenon. By analyzing 12 galaxies with long tadpole-like tails created by tidal forces generated by collisions, the team discovered 425 newborn star clusters, each containing up to a million newborn stars.
Information about star formation
Galactic collisions lead to the formation of gas clouds that, when colliding and collapsing, create a high-pressure environment favorable to the birth of stars. Although the interiors of galactic mergers have been widely studied, less was known about possible star formation in the debris resulting from these mergers, such as in tidal tails. When galaxies interact, gravitational tidal forces tear off long filaments of gas and dust. The gravitational struggle between interacting galaxies stretches the galaxy’s spiral arm like candy, and the star clusters along the tail look almost like a string of pearls. Two known examples of galaxies with these tidal tails are the Antennae and Mouse galaxies, each with long, narrow finger-like projections.
Results and implications of the study.
In the new study, the research team used a combination of new observations and archival Hubble data to determine the age and mass of star clusters within the 12 tidal tails. They then identified the rate of star formation using data from two ultraviolet space telescopes orbiting Earth, one aboard the now-decommissioned Galaxy Evolution Explorer (Galex), and another aboard the Neil Gehrels Swift Observatory, whose Operations Center of Mission is located at Penn State.
The team discovered that many of the star clusters in the tidal tails are very young, only 10 million years old. Furthermore, the clusters appear to form at the same rate along the entire length of the tails, which extend over thousands of light years. The results were published in Monthly Notices of the Royal Astronomical Society.
Before mergers, galaxies were rich in clouds of molecular hydrogen dust that could remain inert. When the clouds collided and collided with each other during the collision, the hydrogen was compressed to the point of triggering a storm of star birth.
According to the researchers, the fate of these elongated groups is uncertain. They could remain gravitationally intact and evolve into globular star clusters, like those orbiting outside the plane of our Milky Way galaxy. Or they could disperse to form a halo of stars around a spiral galaxy or be ejected to become wandering intergalactic stars.
It is thought that star clusters in tidal tails may have been more common in the early universe, when the universe was smaller and galactic collisions were more frequent.
The research team and funding.
The Penn State research team also included Caryl Gronwall, research professor of astronomy and astrophysics, and Yuexing Li, associate professor of astronomy and astrophysics. Also joining the team were Sanchayeeta Borthakur and Karen Knierman from Arizona State University; Aparna Chitré of the Space Telescope Science Institute; Patrick R. Durrell of Youngstown State University; Debra Elmegreen of Vassar College; Jayanne English of the University of Manitoba; Sarah Gallagher of the University of Western Ontario; Iraklis Konstantopoulos, independent academic in New Zealand; Moupiya Maji of the Indian Inter-University Center for Astronomy and Astrophysics; Brendan Mullan of Carnegie Mellon University; Gelys Trancho of the International Thirty Meter Telescope Observatory; and William Vacca of NASA Ames Research Center.