in Dying Galaxies for the First Time
ALMA | NRAO | 2021 Jul 29
ALMA data proves that ram pressure stripping doesn’t spell an immediate end for galaxies
A new study from scientists using the Atacama Large Millimeter/submillimeter Array (ALMA) suggests that previously displaced gases can re-accrete onto galaxies, potentially slowing down the process of galaxy death caused by ram pressure stripping, and creating unique structures more resistant to its effects.
- This side-by-side composite shows ALMA (red/orange) data laid over Hubble (optical) images of NGC 4921. A new study of the spiral bar galaxy revealed filament structures similar to the Pillars of Creation but significantly larger. These structures are caused by a process known as ram pressure stripping, which pushes gas out of galaxies, leaving them without the material needed to form new stars. Credit: ALMA (ESO/NAOJ/NRAO)/S. Dagnello (NRAO), NASA/ESA/Hubble/K. Cook (LLNL), L. Shatz
“Much of the previous work on ram pressure stripped galaxies is focused on the material that gets stripped out of galaxies. In this new work we see some gas that rather than being thrown out of the galaxy never to return is instead moving like a boomerang, being ejected out but then circling around and falling back to its source,” said William Cramer ... “By combining Hubble and ALMA data at very high resolution, we are able to prove that this process is happening.” ...
“We’ve seen in simulations that not all of the gas being pushed by ram pressure stripping escapes the galaxy because it has to reach escape velocity in order to actually escape and not fall back. The re-accretion that we’re seeing, we believe is from clouds of gas that were pushed out of the galaxy by ram pressure stripping, and didn’t achieve escape velocity, so they’re falling back,” said Jeff Kenney ... “If you’re trying to predict how fast a galaxy is going to stop forming stars over time and transform into a red, or dead galaxy, then you want to understand how effective ram pressure is at stripping the gas out. If you don’t know that gas can fall back onto the galaxy and continue to recycle and form new stars, you’re going to overpredict the quenching of the stars. Having proof of this process means more accurate timelines for the lifecycle of galaxies.” ...
Molecular gas filaments and fallback in the ram pressure stripped Coma spiral NGC 4921 ~ William J. Cramer et al
- arXiv.org > astro-ph > arXiv:2107.11731 > 25 Jul 2021