Significant enhancement of ${\rm H_2}$ formation in disk galaxies under strong ram pressure

TL;DR

This study demonstrates that strong ram-pressure can temporarily boost ${\rm H_2}$ formation in disk galaxies by compressing ${\rm H}$ { extsc i}, with the effect influenced by galaxy and cluster properties, before gas stripping reduces ${\rm H_2}$ levels.

Contribution

First numerical investigation showing how ram-pressure enhances ${\rm H_2}$ formation in disk galaxies through gas compression, considering various galaxy and cluster parameters.

Findings

Ram-pressure causes ${\rm H}$ { extsc i} compression, increasing ${\rm H_2}$ formation.

${\rm H_2}$ enhancement depends on cluster mass, galaxy orbit, and disk inclination.

Dust growth is crucial for ${\rm H}$ { extsc i} and ${\rm H_2}$ evolution under ram-pressure.

Abstract

We show, for the first time, that ${\rm H_2}$ formation on dust grains can be enhanced in disk galaxies under strong ram-pressure (RP). We numerically investigate how the time evolution, of ${\rm H}$ {\sc i} and ${\rm H_2}$ components in disk galaxies orbiting a group/cluster of galaxies, can be influenced by hydrodynamical interaction between the gaseous components of the galaxies and the hot intra-cluster medium (ICM). We find that compression of ${\rm H}$ {\sc i} caused by RP increases ${\rm H_2}$ formation in disk galaxies, before RP rapidly strips ${\rm H}$ {\sc i}, cutting off the fuel supply and causing a drop in ${\rm H_2}$ density. We also find that the level of this ${\rm H_2}$ formation enhancement in a disk galaxy under RP depends on the mass of its host cluster dark matter (DM) halo, initial positions and velocities of the disk galaxy, and disk inclination angle with respect to the orbital plane. We demonstrate that dust growth is a key factor in the evolution of the ${\rm H}$ {\sc i} and ${\rm H_2}$ mass in disk galaxies under strong RP. We discuss how the correlation between ${\rm H_2}$ fractions and surface gas densities of disk galaxies evolves with time in the galaxies under RP. We also discuss whether or not galaxy-wide star formation rates (SFRs) in cluster disk galaxies can be enhanced by RP if the SFRs depend on ${\rm H_2}$ densities.