N-body simulations of the Sextans dwarf spheroidal galaxy: accretion at small scales?

In this thesis I produce models based on N-body simulations of the dwarf spheroidal galaxy Sexants, which exhibits a peculiar ring-like feature in its line-of-sight (l.o.s.) velocity and pseudo-equivalent widths of the Mg-triplet absorption feature distributions, as identified by Cicuéndez and Battaglia (2018) using spectroscopic data. Cicuéndez and Battaglia (2018) suggested that these anomalies may be attributed to the accretion of a smaller satellite system, prompting us to conduct N -body simulations to test this hypothesis. The project comprises three main components: the development of a Python software to generate initial conditions (ICs) for the simulations, the execution of simulations under two scenarios (one with a satellite composed only of stars and another satellite composed also of dark matter (DM) halo), and the creation of mock datasets for comparison with observational data. Sextans is modelled with two components - stars and a DM halo - based on literature values. When the satellite is only composed of stars, it is intended to represent a sort of disrupted nuclear star cluster, when it is composed also of DM it is intended to mirror a dwarf satellite galaxy. The simulations are run using the state-of-the-art hydrodynamical N-body code Arepo, exploring different sets of orbital ICs. The results show that, for a satellite initially set in the outskirts of the galaxy, only the simulations involving a satellite with a DM halo successfully replicate, at the same time, the observed ring-like structure and peculiar kinematics in the velocity map. In contrast, simulations without DM failed to reproduce the observed structures. These findings support the hierarchical merging theory at the scale of dwarf galaxies, suggesting that the peculiar features of Sextans can indeed be attributed to an accretion of a smaller system.