Study solved the galaxy murder mystery

What's killing galaxies?


In the most extreme regions of the Universe, galaxies are being killed. Their star formation is being shut down, and astronomers now know the reason.

A new study offers evidence that the extreme environments surrounding galaxies can reach far within them and steal their molecular gas. This molecular gas acts as a fuel for star birth.

The study presents state-of-the-art observations of molecular gas in 51 galaxies belonging to the Virgo Cluster. It’s the first paper released from the Virgo Environment Traced in Carbon Monoxide Survey (VERTICO), undertaken using the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile.

Co-author Dr. Claudia Lagos, ASTRO 3D Senior Research Fellow at ICRAR-UWA, said, “We know that galaxies in the most extreme environments suffer tremendously, losing their gas reservoirs and eventually being unable to form any more stars. For a galaxy, that’s the equivalent of dying. VERTICO offers us an unprecedented window on how the molecular gas, the direct fuel for new stars, is affected, allowing us to diagnose what’s killing those galaxies effectively.”

NGC 4567 and NGC 4568
NGC 4567 and NGC 4568 are 2 of the 2,000 galaxies in the Virgo Cluster, located roughly 65 million light-years from Earth. Observed by the VERTICO—Virgo Environment Traced in Carbon Monoxide—Survey, the 2 galaxies are among those in the galaxy cluster impacted by extreme physical processes that can lead to the death of galaxies. The galaxies are shown here in composite radio data from ALMA with molecular gas in red/orange and optical data from the Hubble Space Telescope with stars in white/blue. Credit: ALMA (ESO/NAOJ/NRAO)/S. Dagnello (NRAO)

The galaxy’s location and its interaction with its surroundings influence the ability of the galaxy to form stars. Galaxy clusters are massive, hottest, and most extreme among many different environments in the Universe. They are the perfect cosmic laboratory for observations such as VERTICO.

The nearby Virgo Cluster is seven million light-years across and contains thousands of galaxies hurtling through the superheated plasma at speeds of up to several million kilometers per hour. It is an environment so extreme and inhospitable that entire galaxies can be stopped from forming stars in a process known as galaxy quenching. Not to worry though, our own Milky Way galaxy is nowhere near any cluster and isn’t in any danger of having its gas stripped away.

Lagos said, “With VERTICO, we looked at the gas reservoir of 51 galaxies in the Virgo Cluster, one of the most extreme environments we know of. We were able to create among the most detailed maps of gas distribution in cluster galaxies ever observed. These images provide the missing pieces of the puzzle of how the environment affects the gas content of galaxies, especially the dense and cold gas, and hence their ability to form stars.”

Scientists found that the cluster environment left an imprint on their gas disks. This is the clearest evidence that surrounding environmental mechanisms reach far into galaxies to disturb and perturb their molecular gas and impact their star formation.

Lead author Dr. Toby Brown, ICRAR alumnus and Plaskett Fellow at the National Research Council of Canada, said“Gas stripping is one of the most spectacular and violent external mechanisms that can shut down star formation in galaxies. Gas stripping occurs when galaxies are moving so fast through hot plasma in the cluster that vast quantities of cold molecular gas are stripped from the galaxy – as though the gas is being swept away by a huge cosmic broom. The exquisite quality of VERTICO’s observations allows us to see better and understand such mechanisms.”

The study offers essential data to better understand the way star formation and galaxy evolution occurs in the most extreme environments in the Universe.

Journal Reference:
  1. Toby Brown et al. VERTICO: The Virgo Environment Traced In CO Survey. DOI: 10.3847/1538-4365/ac28f5
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