Jellyfish galaxies with the IllustrisTNG simulations -- When, where, and for how long does ram pressure stripping of cold gas occur?

Abstract

Jellyfish galaxies are prototypical examples of satellite galaxies undergoing strong ram pressure stripping (RPS). We analyze the evolution of 512 unique, first-infalling jellyfish galaxies from the TNG50 cosmological simulation. These have been visually inspected to be undergoing RPS sometime in the past 5 billion years (since $z=0.5$), have satellite stellar masses $\mstarsat\sim10^{8-10.5}\,M_\odot$, and live in hosts with $\mvir\sim10^{12-14.3}\,M_\odot$ at $z=0$. We quantify the cold gas ($T\leq10^{4.5}$ K) removal using the tracer particles, confirming that for these jellyfish, RPS is the dominant driver of cold gas loss after infall. Half of these jellyfish are completely gas-less by $z=0$, and these galaxies have earlier infall times and smaller satellite-to-host mass ratios than their gaseous counterparts. RPS can act on jellyfish galaxies over long time scales of $\approx1.5-8$ Gyr. Jellyfish in more massive hosts are impacted by RPS for a shorter time span and, at a fixed host mass, jellyfish with less cold gas at infall and lower stellar masses at $z=0$ have shorter RPS time spans. While RPS may act for long periods of time, the peak RPS period -- where at least 50 pecent of the total RPS occurs -- begins within $\approx1$ Gyr of infall and lasts $\lesssim2$ Gyr. During this period, the jellyfish are at host-centric distances $\sim0.2-2\rvir$, illustrating that much of RPS occurs at large distances from the host galaxy. Interestingly, jellyfish continue forming stars until they have lost $\approx98$ percent of their cold gas. For groups and clusters in TNG50 $(\mvirhost\sim10^{13-14.3}\,M_\odot)$, jellyfish galaxies deposit more cold gas ($\sim10^{11-12}\,M_\odot$) into halos than exist in them at $z=0$, demonstrating that jellyfish, and in general satellite galaxies, are a significant source of cold gas accretion.