Ram-pressure stripped galaxies in galactic-scale simulations

Galaxies are complex systems that do not simply exist in isolation but are influenced by the environment in which they reside, particularly in rich clusters. Ram-pressure stripping (RPS) is one of environmental mechanisms that can promote both morphological and colour evolution of a galaxy. RPS removes the gas from galaxy infalling into a cluster which in turn leads to star-formation quenching. This Thesis aims to explore the evolution of RPS galaxies using high-resolution galaxy-scale simulations, and improve our understanding of the processes happening in these peculiar objects. I run a suite of wind-tunnel hydrodynamical simulations of a massive disc galaxy falling into a massive cluster. The simulations include star formation and stellar feedback. I simulate four realisations of the same galaxy subject to the same intracluster medium (ICM) wind that hits the galaxy at different angles: face-on, edge-on and angled at 45º, and an control isolated galaxy. First, I study whether RPS can enhance accretion onto a central black hole (BH) and trigger an active galactic nucleus (AGN). I find that RPS increases the inflow of gas to the galaxy centre regardless of the wind impact angle. I identify the mechanisms that drive the inflow as the mixing of interstellar medium (ISM) and non-rotating ICM and pressure torques. I also estimate the BH accretion using three accretion models. Although their parameters were chosen to estimate similar accretion rates in an isolated galaxy, all three models give different results in the galaxies subject to RPS. I argue that the commonly used accretion models cannot account for the RPS-induced mechanisms of gas transport. Next, I evaluate the role of star formation and stellar feedback in gas stripping. I use the same set of four star-forming galaxies, and simulate four other radiative-cooling-only (RC) identical galaxies. I directly compare the stripping evolution of galaxies with and without star formation. I find that stellar feedback has no direct effect on the stripping process. Instead, it homogenises the ISM, which makes the stripping proceed in an outside-in way in line with observations. The density distribution in a RC galaxies is dominated by overdense clumps embedded in low-density ‘holes’, and stripping is under- and overestimated in certain parts of a galaxy, leading to an overall erroneous picture of RPS. Overall, in a massive galaxy the effect of stellar feedback on the stripping rate is almost negligible. I also study in-situ star formation in the stripped tails, using the face-on and angled-wind galaxies from the same set of simulations. Generally, stars are formed as a result of outside-in stripping. They have decreasing metallicities the farther they are from the disc as a result of gradual mixing between ISM and ICM. Not all stars follow this model, and there is a population of stars born from the gas that is falling back onto the galaxy. These stars can arrange themselves into ‘inverse fireballs’. Almost all of the tail stars will fall on the galaxy, and will not contribute to the intracluster light. I present images that mock UV observations, which show that the vertical distribution of stars in galaxies that have been completely stripped is not significantly broader than in an isolated galaxy. Finally, I present a new set of simulations that include a BH particle with AGN feedback in the form of jets. The initial conditions and overall set-up and identical to the previous simulations, and I directly compare evolution of galaxies with and without a BH. The actual BH particles accrete more gas than what is analytically estimated in the simulations without a BH. AGN feedback acts to suppress star formation globally, evidence suggests that it also prevents ICM accretion onto the galaxy. I also simulate a galaxy subject to face-on ICM wind, and find that a galaxy with a BH is stripped slower than a galaxy without one independently of how often AGN feedback is ejected.