Simulating Jellyfish Galaxies: A Case Study for a Gas-Rich Dwarf Galaxy

TL;DR

This study uses radiation-hydrodynamic simulations to explore how gas-rich dwarf galaxies develop jellyfish-like features through ram-pressure stripping, revealing the origins of molecular clumps, star formation, and emission properties in the tails.

Contribution

It provides a detailed simulation-based analysis of jellyfish galaxy formation, highlighting the roles of ISM-ICM mixing and in-situ star formation in tail development.

Findings

Most molecular clumps in the near wake originate from RPS ISM.

Star formation occurs mainly within 10 kpc of the galactic plane in the tail.

Stripped tails show intermediate X-ray to Hα surface brightness ratios.

Abstract

We investigate the formation of jellyfish galaxies using radiation-hydrodynamic simulations of gas-rich dwarf galaxies with a multi-phase interstellar medium (ISM). We find that the ram-pressure-stripped (RPS) ISM is the dominant source of molecular clumps in the near wake within 10 kpc from the galactic plane, while in-situ formation is the major channel for dense gas in the distant tail of the gas-rich galaxy. Only 20% of the molecular clumps in the near wake originate from the intracluster medium (ICM); however, the fraction reaches 50% in the clumps located at $80\,{\rm kpc}$ from the galactic center since the cooling time of the RPS gas tends to be short due to the ISM--ICM mixing ($\lesssim$ 10 Myr). The tail region exhibits a star formation rate of $0.001-0.01\,{\rm M_{\odot}\,yr^{-1}}$, and most of the tail stars are born in the stripped wake within 10 kpc from the galactic plane. These stars induce bright H$\alpha$ blobs in the tail, while H$\alpha$ tails fainter than $6\times10^{38}\,{\rm erg\,s^{-1}\,kpc^{-2}}$ are mostly formed via collisional radiation and heating due to mixing. We also find that the stripped tails have intermediate X-ray to H$\alpha$ surface brightness ratios (1.5$\lesssim F_{\rm X}/F_{\rm H\alpha}\lesssim$20), compared to the ISM ($\lesssim$1.5) or pure ICM ($\gg$20). Our results suggest that jellyfish features emerge when the ISM from gas-rich galaxies is stripped by strong ram pressure, mixes with the ICM, and enhances the cooling in the tail.