The Gas Metallicity of Ram-Pressure Stripped Galaxies at Intermediate Redshifts with MUSE Data

The purpose of this thesis is to examine how ionized gas metallicity is distributed in ram-pressure stripped (RPS) galaxies in clusters at intermediate redshifts. The ram pressure exerted by the hot intracluster medium on the galaxy's interstellar medium can efficiently remove gas from galaxies in massive dark matter haloes, and it is considered the most important physical process for the evolution of cluster galaxies. At low redshifts, it has been shown that RPS galaxies often display extraplanar tails of ionized stripped gas, which can reach several tens of kpc away from the disk. At higher redshifts, in the last few years, there have been a few works find- ing clear signatures of RPS tails, but a study of the gas metallicities of RPS galaxies in distant clusters has not been conducted so far. By analyzing the distribution of metallicity in these galaxies, we hope to gain insight into the physical processes responsible for the observed chemical compositions and how they change over time in galaxy clusters. Additionally, we aim to establish a correlation between gas-phase metallicity and other galaxy characteristics, such as stellar mass, in the presence of ram pressure stripping. Spatially resolved studies of gas metallicities, their dependence on galaxy environment, and their evolution can enhance our comprehension of the intricate interplay of physical mechanisms that have influenced the characteristics of galaxies over the course of cosmic history. In this work, I study the RPS galaxies classified by Moretti et al. (2022) in the first two ob- served clusters, Abell2744 and Abell370, within the MUSE-GTO program at redshifts 0.308 and 0.375 (Richard et al., 2021). I investigate the spatially-resolved metallicities of galactic disks and stripped-out tails by employing both theoretical methods, such as photoionization models, and empirical calibrations. Moreover, by obtaining the representative median metallicity values of disks and tails as well as integrating each galaxy’s disk and tail spectra, I study the global gas-phase metallicity and its relation with other galaxy characteristics. Initially, I explore the metallicity trend along the disks and tails of individual galaxies. In certain instances, the metallicity can be measured only in the vicinity of the outer edges of the disk, while in other cases it is detected much farther away, up to a distance of around 50kpc from the disk. Then, I examine the spatially-resolved mass-metallicity relation (rMZR) in RPS galaxies for the subset of galaxies where the stellar-continuum emission is sufficiently bright to determine the spatially resolved stellar mass surface density. Next, I determine the global mass- metallicity relation (MZR) using two distinct approaches: stacking the spectra of each galaxy’s disk and tail separately and calculating their median metallicities as a representative value of each disk and tail. In general, the observed metallicity trend with projected distance indicates that the gradients in disks tend to be either negative or flat, while gradients in tails are typically negative, with varying slopes that may be influenced by projection effects. Additionally, massive galaxies (with log(M)> 9.7) have tails with metallicities lower than anywhere in their disks. On the other hand, galaxies with the lowest masses (log(M)∼ 8) exhibit a uniform, flat gradient across both their disk and tail. Furthermore, this study indicates that the rMZR of the disks and tails are generally flat or positive, with tail spaxels consistently displaying lower surface mass densities compared to their disk counterparts.