Ram Pressure Stripping of Molecular Gas

Abstract

Ram pressure stripping (RPS) can be described as the constant wind a galaxy experiences when moving through a galaxy cluster. It is well-established that galaxies undergoing this process lose substantial amounts of their atomic gas, but its effect on the cold molecular gas component is still not fully understood. Using high-resolution ALMA CO 2-1 data collected by the PHANGS and VERTICO surveys, I model the detailed effect of RPS in 36 Virgo galaxies on a 150 pc and 720 pc scale by calculating the ratio of ram pressure to the galaxy gravitational restoring force per unit area. If the ram pressure exceeds the restoring pressure, we assume the molecular gas parcel is susceptible to stripping. I reveal that roughly a quarter of our 36 galaxies are susceptible to molecular gas RPS, with up to 70% of their molecular gas in the outer disk (r > R50) being susceptible. As expected, low mass galaxies (log(M∗/M ) = 9.5) seem to be most affected. VERTICO galaxies show molecular gas susceptible to stripping at the outskirts and between their spiral arms. I also find higher fractions of RPS susceptible molecular gas in galaxies exhibiting clear atomic gas tails, suggesting that RPS impacts multiple gas phases at once. Finally, a phase space analysis suggests molecular gas RPS occurs primarily, potentially exclusively, at the first pericentric passage when ram pressure is maximal.