The coupling between the core/cusp and missing satellite problems

TL;DR

This paper investigates the energy requirements and physical processes needed to resolve the core/cusp and missing satellite problems in cold dark matter models, emphasizing the role of baryonic feedback and star formation history.

Contribution

It quantifies the energy needed to create cores in dwarf galaxy halos and discusses the implications for star formation efficiency and feedback mechanisms in CDM models.

Findings

Supernova feedback can generate cores but is limited by star formation efficiency.

Large cores in luminous dwarfs imply high-redshift star formation or efficient energy coupling.

Tensions between core formation and satellite abundance constraints are highlighted.

Abstract

We calculate the energy that baryons must inject in cold dark matter (CDM) haloes in order to remove centrally-divergent DM cusps on scales relevant to observations of dwarf spheroidal galaxies (dSphs). We estimate that the CDM haloes often associated with the Milky Way's dSphs (M_vir/M_\odot \sim 10^{9-10}) require \Delta E/erg \sim 10^{53-55} in order to form cores on scales comparable to the luminous size of these galaxies. While supernova type II (SNeII) explosions can in principle generate this energy, the actual contribution is limited by the low star formation efficiency implied by the abundance of luminous satellites. Considering that CDM's well-known `core/cusp' and `missing satellite' problems place opposing demands on star formation efficiencies, existing observational evidences for large cores in the most luminous dSphs require that CDM models invoke some combination of the following: (i) efficient (of order unity) coupling of SNeII energy into dark matter particles, (ii) star formation histories peaking at unexpectedly high redshifts (z>6), (iii) a top-heavy stellar IMF, and/or (iv) substantial satellite disruption or other stochastic effects to ease the substructure abundance constraints. Our models show that the tension between CDM problems on small scales would increase if cored DM profiles were to be found in fainter dwarves.