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

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 $80\mathrm{kpc}$ 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 $0.001-0.01{\mathrm{M}}_{\odot }\mathrm{y}{\mathrm{r}}^{-1}$, and most of the tail stars are born in the stripped wake within 10 kpc from the galactic plane. These stars induce bright H$\hat{I}\pm$ blobs in the tail, while H$\hat{I}\pm$ tails fainter than $6\times 10^{38}\mathrm{erg}{\mathrm{s}}^{-1}\mathrm{kp}{\mathrm{c}}^{-2}$ are mostly formed via collisional radiation and heating due to mixing. We also find that the stripped tails have intermediate X-ray to H$\hat{I}\pm$ surface brightness ratios (1.5$\lesssim F_{\mathrm{X}}/F_{\mathrm{H}\hat{\mathrm{I}}\pm }\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.

19 pages, 15 figures; Accepted for publication in ApJ