The Tail of the Stripped Gas that Cooled: HI, Halpha and X-ray Observational Signatures of Ram Pressure Stripping

TL;DR

This study uses hydrodynamical simulations with radiative cooling to explore the observable signatures of gas tails formed by ram pressure stripping in galaxies, predicting detectable H I and Halpha emissions but not X-ray emissions.

Contribution

It introduces detailed hydrodynamical simulations including radiative cooling to model the morphology and emission signatures of ram pressure stripped gas tails.

Findings

Radiative cooling produces narrower, more realistic gas tails.

H I and Halpha emissions are likely detectable from the tails.

X-ray emission from the tails is generally not observable.

Abstract

Galaxies moving through the intracluster medium (ICM) of a cluster of galaxies can lose gas via ram pressure stripping. This stripped gas forms a tail behind the galaxy which is potentially observable. In this paper, we carry out hydrodynamical simulations of a galaxy undergoing stripping with a focus on the gas properties in the wake and their observational signatures. We include radiative cooling in an adaptive hydrocode in order to investigate the impact of a clumpy, multi-phase interstellar medium. We find that including cooling results in a very different morphology for the gas in the tail, with a much wider range of temperatures and densities. The tail is significantly narrower in runs with radiative cooling, in agreement with observed wakes. In addition, we make detailed predictions of H I, Halpha and X-ray emission for the wake, showing that we generally expect detectable H I and Halpha signatures, but no observable X-ray emission (at least for our chosen ram-pressure strength and ICM conditions). We find that the relative strength of the Halpha diagnostic depends somewhat on our adopted minimum temperature floor (below which we set cooling to zero to mimic physics processes not included in the simulation).