Dark influences: imprints of dark satellites on dwarf galaxies

Abstract

In the context of the current $\Lambda$CDM cosmological model small dark matter haloes are abundant and satellites of dwarf galaxies are expected to be predominantly dark. Since low mass galaxies have smaller baryon fractions interactions with these satellites may leave particularly dramatic imprints. We uncover the influence of the most massive of these dark satellites on disky dwarf galaxies and the possible dynamical and morphological transformations that result from these interactions. We use a suite of carefully set-up, controlled simulations of isolated dwarf galaxies. The primary dwarf galaxies have solely a stellar disk in the dark matter halo and the secundaries are completely devoid of baryons. We vary the disk mass, halo concentration, initial disk thickness and inclination of the satellite orbit. The disky dwarf galaxies are heated and disrupted due to the minor merger event, more extremely for higher satellite over disk mass ratios, and the morphology and kinematics are significantly altered. Moreover, for less concentrated haloes the minor merger can completely destroy the disk leaving a low-luminosity spheroidal-like galaxy instead. We conclude that dwarf galaxies are very much susceptible to being disturbed by dark galaxies and that even a minor merger event can significantly disrupt and alter the structure and kinematics of a dwarf galaxy. This process may be seen as a new channel for the formation of dwarf spheroidal galaxies.