Astronomers Discover What’s Killing Galaxies

Astronomers examining the nearby Universe with the help of the Atacama Large Millimeter / submillimeter Array (ALMA) have just completed the largest high-resolution star-forming fuel survey ever conducted in galaxy clusters. But, more importantly, they’re dealing with an ancient astrophysical mystery: what’s killing galaxies? The research, which provides the clearest evidence to date that extreme environments in space have severe impacts on galaxies within them, will be published in an upcoming issue of The Astrophysical Journal Supplement Series.

The program called Virgo Environment Traced in Carbon Monoxide Survey, or VERTICO, aimed to better understand the formation of stars and the role of galaxies in the universe. “We know that galaxies are being killed by their environments and we want to know why,” said Toby Brown, Plaskett Fellow at the National Research Council of Canada and lead author of the paper. “What VERTICO reveals better than ever is what physical processes affect the molecular gas and how they dictate the life and death of the galaxy.”

Galaxies are large collections of stars, and their births, evolutions, and deaths are influenced by where they live in the Universe and how they interact with their surroundings. Galaxy clusters, in particular, are some of the most extreme environments in the Universe, making them of particular interest to scientists studying the evolution of galaxies.

Home to thousands of galaxies, the Virgo Cluster is the closest massive cluster of galaxies to the Local Group, where the Milky Way resides. The extreme size and proximity make the cluster easy to study, but it also has other characteristics that make it suitable for observation. “The Virgo cluster is a bit unusual in that it has a relatively large population of galaxies that are still forming stars,” said Christine Wilson, a professor at McMaster University and co-principal researcher on the VERTICO project. “Many galaxy clusters in the Universe are dominated by red galaxies with little gas and star formation.”

The VERTICO project observed the gas reservoirs of 51 galaxies in the Virgo cluster at high resolution, revealing an environment so extreme and inhospitable that it could prevent entire galaxies from forming stars in a process known as galaxy extinction. “The Virgo cluster is the most extreme region of the local Universe, filled with a million degrees plasma, extreme galaxy speeds, violent interactions between galaxies and their surroundings, a galaxy retreat village and, consequently, a galaxy graveyard ” Brown said, adding that the project has revealed how removing gas can paralyze or paralyze one of the most important physical processes in the Universe: the formation of stars. “Gas removal is one of the most spectacular and violent external mechanisms that can interrupt star formation in galaxies,” Brown said. “Gas removal occurs when galaxies are moving so fast through the hot plasma in the cluster that vast amounts of cold molecular gas are removed from the galaxy, as if the gas were being swept away by an enormous cosmic broom. The excellent quality of VERTICO’s observations allows us to see and better understand these mechanisms.”

The project was aided by ALMA’s Band 6 receiver – developed at the Central Development Laboratory of the National Radio Astronomy Observatory (CDL) – which provides high sensitivity and high resolution, minimizing the necessary observation time. This, in turn, has led to the collection of a significant amount of data, which may contain the clues needed to solve the remaining mysteries of how environments impact galaxies and, consequently, how galaxies die. Wilson said: “There have been many questions over the years about whether and how the cluster environment affects the molecular gas in galaxies, and how exactly these environments might contribute to their demise. We still have work to do, but I’m confident VERTICO will allow us to answer these questions once and for all.”

The new article is VERTICO’s first, with additional research planned for publication in the near future.