Stripped of Gas, Galaxies Die

Nov 22, 2021 | Daily Space, Galaxies

Stripped of Gas, Galaxies Die
IMAGE: In this composite image, ALMA’s radio wavelength observations of the VERTICO galaxies’ molecular gas disks are magnified by a factor of 20. They are overlaid on the X-ray image of the hot plasma within the Virgo Cluster. CREDIT: ALMA (ESO/NAOJ/NRAO)/S. Dagnello (NRAO)/Böhringer et al. (ROSAT All-Sky Survey)

I have to start this story by admitting that I wanted to discuss it because the data used looks more like an artist’s impression of a galaxy cluster than like an actual image.

In a new paper coming out in The Astrophysical Journal Supplement, researchers led by Toby Brown release an amazing map of the Virgo Galaxy Cluster that traces the presence of carbon monoxide in and around this cluster’s galaxies. The goal was straight forward – to track down the physics responsible for killing star formation in galaxies that plunge into galaxy clusters.

Galaxies like our own Milky Way galaxy will one day become.

According to Brown: We know that galaxies are being killed by their environments, and we want to know why.

The big picture of what is going on has been known for decades: as a galaxy falls into the high-density environment of a cluster, it takes on a series of enemies. On one hand, the intracluster gas is pushing on the infalling galaxies, and through a process called ram pressure stripping, those galaxies get their star-forming material pushed out. Infalling galaxies also go through increasing numbers of close encounters with other galaxies, and these high speed encounters gravitationally pull more material out of systems through a process called galaxy harassment.

The language of galaxy interactions is violent, and every violent encounter leaves galaxies with less material to form stars. Brown explains: Gas stripping is one of the most spectacular and violent external mechanisms that can shut down star formation in galaxies.

While we’ve understood these big picture ideas for a long time, the details of what this looks like haven’t been known. It is only with this new survey by ALMA that seeing the details has become possible. Called The Virgo Environment Traced in Carbon Monoxide Survey — VERTICO — this campaign has imaged the gas reservoirs of 51 galaxies in high resolution.

This new paper is the catalogue of data, and science papers will be coming in the months and years to come as folks take the time to analyze each of these 51 galaxies. Already hints of what is to come can be seen in the mapping of interacting systems and in the knots of gas seen in isolated systems.

Using this catalogue, researchers will be able to see what galaxies at different points in falling into the cluster look like. They’ll be able to study those solitary systems, and interacting systems. And just like it is possible to piece together how humans age by looking at all the people in the mall on a Saturday afternoon and seeing individuals of every age, we will be able to piece together how galaxies die by seeing how they change at every step of falling into the cluster.

This is beautiful data, and it is going to allow for amazing science, and I am here for it. As new results come out, we’ll bring them to you here on the Daily Space.

More Information

What’s Killing Galaxies? Solving a Long-Standing Mystery in Astrophysics (SciTechDaily)

VERTICO: The Virgo Environment Traced in CO Survey,” Toby Brown et al., 2021 November 10, The Astrophysical Journal Supplement Series

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