A possible formation scenario for dwarf spheroidal galaxies – II. A parameter study

Abstract

Dwarf spheroidal (dSph) galaxies are considered the basic building blocks of the galaxy formation process in the Lambda cold dark matter hierarchical cosmological model. These galaxies are believed to be the most dark matter (DM) dominated systems known, have the lowest stellar content and are poor in gas. Many theories attempt to explain the formation of dSph galaxies resorting to the fact that these galaxies are mainly found orbiting large galaxies or invoking other mechanisms of interactions. Here, we show the full set of simulation as an extension of our fiducial model, where we study the formation of classical dSph galaxies in isolation by dissolving star clusters within the DM halo of the dwarf galaxy. In our parameter survey, we adopt cored and cusped DM halo profiles and consider different numbers of dissolving star clusters.We investigate the dependence of observable quantities with different masses and scalelengths of the DM halo and different star formation efficiencies.We find that our proposed scenario explains many features of the classical dSph galaxies of theMilkyWay, like their morphology and their dynamics. We see trends how the surface brightness and the scalelength of the luminous component vary with the parameters of our simulations. We also identify how irregularities in their shape, i.e. clumpiness and ellipticity vary in our simulations. In velocity space, we identify the parameters leading to flat velocity dispersions curves. We recognize kinematically cold substructures in velocity space, named fossil remnants and stemming from our unique initial conditions, which alter the expected results. These streaming motions are considered as a key feature for future observation with high resolution to validate our scenario.