Comparing the interstellar and circumgalactic origin of gas in the tails of jellyfish galaxies

TL;DR

This study uses magneto-hydrodynamical simulations to reveal that most gas in jellyfish galaxy tails originates from the circumgalactic medium, challenging the idea that it mainly comes from the interstellar medium.

Contribution

The paper demonstrates through simulations that the circumgalactic medium significantly contributes to jellyfish galaxy tails, contrasting previous assumptions about their origin.

Findings

Most tail gas originates from the circumgalactic medium.

Gas metallicity in the tail decreases with distance from the galaxy.

Both ISM and CGM contribute to tail formation after cluster passage.

Abstract

Simulations and observations find long tails in jellyfish galaxies, which are commonly thought to originate from ram-pressure stripped gas of the interstellar medium (ISM) in the immediate galactic wake. While at larger distances from the galaxy, they have been claimed to form in situ owing to thermal instability and fast radiative cooling of mixed ISM and intracluster medium (ICM). In this paper, we use magneto-hydrodynamical windtunnel simulations of a galaxy with the arepo code to study the origin of gas in the tails of jellyfish galaxies. To this end, we model the galaxy orbit in a cluster by accounting for a time-varying galaxy velocity, ICM density and turbulent magnetic field. Tracking gas flows between the ISM, the circumgalactic medium (CGM) and the ICM, we find contrary to popular opinion that the majority of gas in the tail originated in the CGM. Prior to the central passage of the jellyfish galaxy in the cluster, the CGM is directly transported to the clumpy jellyfish tail that has been shattered into small cloudlets. After the central cluster passage, gas in the tail originates both from the initial ISM and the CGM, but that from the latter was accreted to the galactic ISM before being ram-pressure stripped to form filamentary tentacles in the tail. Our simulation shows a declining gas metallicity in the tail as a function of downstream distance from the galaxy. We conclude that the CGM plays an important role in shaping the tails of jellyfish galaxies.