Gas metallicity of ram-pressure-stripped galaxies at intermediate redshifts with MUSE data

Abstract

Extraplanar tails of ionized-stripped gas, extending up to several tens of kiloparsecs beyond the stellar disk, are often observed in ram-pressure-stripped (RPS) galaxies in low-redshift clusters. Recent studies have also identified similar tails at high redshifts, and we present here the first analysis of the chemical composition of such tails beyond the local Universe. Specifically, we examined the distribution of the ionized gas metallicity of RPS galaxies in the Abell 2744 (z = 0.308) and Abell 370 (z = 0.375) clusters observed as part of the MUSE-GTO program. We investigated spatially resolved and global metallicities in galactic disks and stripped tails, utilizing both a theoretical calibration from a photoionization model and an empirical calibration. The metallicity gradients and the spatially resolved mass–metallicity relations indicate that the metallicity in the tails reaches values that are up to ∼0.6 dex lower than anywhere in the parent disks, with a few exceptions. Both the disks and tails follow a global mass–metallicity relation, though the tail metallicity is systematically lower than that of the corresponding disk, by up to ∼0.2 dex. These findings demonstrate that additional processes are at play in the tails and are consistent with a scenario of a progressive dilution of the metallicity along the tails due to the mixing of the intracluster medium and interstellar gas, in accordance with previous low-z results. In principle, the same scenario can also explain the flat or positive metallicity gradients observed in low-mass RPS galaxies since in these galaxies the interstellar medium’s metallicity can approach the metallicity levels found in the intracluster medium.