Using data from the Atacama Large Millimeter Array (ALMA), the Combined Array for Research in Millimeter-Wave Astronomy (CARMA), and the NASA / ESA Hubble Space Telescope, astronomers have observed a cosmic boomerang effect: streams of molecular gas disappearing from a later returning galaxy, boomerang effect, in the northwestern quadrant of NGC 4921, a spiral galaxy in the Coma cluster.
The Coma Cluster is a large galaxy cluster containing more than 1000 identified galaxies located 322.9 million light years away from Earth.
With a radius of 10 million light years, this cluster is one of the largest clusters in the Coma Supercluster. Also known as Abell 1656, it is a spectacular place to study ram pressure extraction, a process known to remove gas from galaxies, leaving them without the material needed to form new stars. Now we can see that process in high resolution.
“Astronomers are interested in studying how galaxies grow, live and die,” says William Cramer, a postdoctoral researcher at Arizona State University and a co-author of the work published in the Astrophysical Journal. “Effects such as ram pressure that can accelerate the normal life cycle of the galaxy are very important to understand for this reason. Furthermore, molecular gas in galaxies is the birthplace of new stars and therefore studying the effect of ram pressure on him is of utmost importance. “
The image, a high-resolution map of dense molecular gas in NGC 4921, a massive spiral galaxy, shows unusual structures that form under the pressure of the ram “wind”: long filaments of heavy gas connected to newly formed stars.
The ALMA data clearly show molecular gas filaments connected to NGC 4921; the filaments, in fact, are resisting. But then the astronomer saw something else: some of that expelled gas comes back.
“Instead of being thrown out never to return, some of this gas moves like a boomerang, is expelled but then spins in circles and falls back to its source. If this gas is recaptured in the galaxy, it can form new stars, ”Dr. Cramer said. “The boomerang effect is significant for several reasons. It provides strong evidence on the evolution of galaxies. “
This observation confirms an old hypothesis about the development of galaxies, a rather complex field of astrophysics.
Referencia: William J. Cramer et al. 2021. Molecular gas filaments and fallback in the ram pressure stripped Coma spiral NGC 4921. ApJ, in press; arXiv: 2107.11731
