SN-driven mechanism of cusp-core transformation: an appraisal.

We present and test an effective model for N -body simulations that aims at mimicking the impact of supernova (SN) feedback on the dark matter (DM) distribution of isolated halos hosting dwarf galaxies. Although the model is physically decoupled from the cosmological history of both the DM halo and the dwarf galaxy, it allows us to study the impact of different macroscopic parameters such as galaxy concentration, total feedback energy and energy injection time in the process of SN-driven core formation in a physically clear way. Using our effective model in a suite of N -body simulations of an isolated halo with different SN feedback parameters, we find that whether or not a DM core forms depends primarily on the total amount of injected SN feedback energy. At a fixed injected energy, the size of the DM core is larger the faster the energy injection occurs and the more compact the dwarf galaxy is. Analyzing the orbital evolution of kinematic tracers, we demonstrate that a core forms through SN feedback only if the energy injection is impulsive relative to the dynamical timescale of particles in the inner halo. The converse statement, however, is not true. Consequently, the presence of signatures of impulsive changes of the gravitational potential is not a sufficient condition for dwarf-size halos to have cored density profiles.