Speaker : Dr. Rory Smith
Title : The effects of the cluster environment on dwarf galaxies - ram pressure and harassment.Abstract: Dwarf galaxies that are found in clusters of galaxies face a harsh environment. A multi-million kelvin ionised gas fills the cluster, and bathes the cluster galaxies. As cluster galaxies orbit through this gas, it exerts a 'ram pressure' that can strip away disk gas, and halt their star formation. Simultaneously the deep potential well of the cluster exerts powerful tidal forces, combined with repeated high speed encounters with other cluster galaxies. This effect, known as 'harassment', can strip away dark matter and stars from a cluster galaxy. I will present my results of modelling the effects of ram pressure and harassment on dwarf galaxies using numerical simulations. I will demonstrate how ram pressure, often assumed to only affect the gas of a galaxy, can in fact significantly affect the stars - and even the dark matter - of dwarf galaxies. I will also show how harassment is surprisingly weak acting on cluster dwarfs, despite their very low masses, and that this is due to the orbits they typically have. Finally I will discuss how phase-diagrams may provide a powerful tool to understand both ram pressure and harassment in real galaxy clusters.