Milky Way’s Defensive Halo Blocks Incoming Gas Cloud

Composite image created by Kat Barger, with GBT data represented in orange, using the Milky Way Panorama in the background (background image credit ESO/S. Brunier.)

How are galaxies able to keep forming stars and planets? Astronomers from Texas Christian University are using the Green Bank Telescope to reveal more about this process, studying high-velocity clouds that are being pulled into our Milky Way galaxy by its gravitational pull.

Stars and planets require large amounts of gas to form, and galaxies can run out of this cosmic building material unless they can capture more gas from their surroundings. Obstacles in the way can disrupt and disperse clouds before they conclude their journey.

Texas Christian University physics and astronomy professor Dr. Kat Barger led a team observing Complex A, a high velocity gas cloud containing enough material to make more than 2 million Suns  –  if all of it could reach our Milky Way. However, gas instabilities form along the cloud as parts of it drip through the lower density halo gas that surrounds it. These drips are then sheared off as the high velocity cloud rubs against the halo gas that it is traveling through–essentially acting like a wind tunnel. Gradually, these clouds lose their valuable star and planet building material. Dr. Barger’s team is deciphering how large galaxies like ours will be able to keep making stars and planets over the next billion years to come.

A still from the 3D movie of Complex A’s Hydrogen gas distribution that rotates through position–position–velocity maps. The real-time duration of the movie is 1 minute, 21s. View the animation by clicking on the image. Image credit: Kat Barger, et al.

Astronomers are simulating these gas instability processes that affect these clouds, “Simulations keep getting better, with higher resolution and more physics, but they are still poorly constrained. We still don’t know the details of how exactly these clouds break up, but these observations will help,” says Dr. Barger.

The Green Bank Telescope is an important part of capturing this information. Observations of gas clouds like Complex A, mapped at a high resolution, have only been completed once before. The Green Bank Telescope sensitivity and capacity make research like this possible. Collaborator Dr. David Nidever says that this telescope allows “us to map this large gas cloud in great detail down to the minute undulating features being produced by it’s path onto the Milky Way’s disk”. Dr. Barger is pleased with their progress, “This is the first time that we’ve mapped a gas cloud that did not originate from the Milky Way and that will supply our galaxy with new gas so thoroughly.”

Read more about Dr. Barger’s latest findings, published in the October 2020 issue of the Astrophysical Journal.

Interested in contributing to citizen science? Learn more about research opportunities with Dr. Barger and Texas Christian University, the Green Bank Observatory, and our partners.

The Green Bank Observatory is a facility of the National Science Foundation and is operated by Associated Universities, Inc.

This release was shared during a press conference at the 237th meeting of the American Astronomical Society.



Dr. Kat Barger, Associate Professor, Texas Christian University  ude.u1716987781ct@re1716987781grab.1716987781k1716987781

Jill Malusky, Green Bank Observatory Public Relations, ude.o1716987781arn@y1716987781ksula1716987781mj1716987781