Overlay of the Special Issue 'The Role of Halo Substructure in Gamma-Ray Dark Matter Searches'

Abstract

An important open question today is the understanding of the relevance that dark matter (DM) halo substructure may have for DM searches. In the standard cosmological framework, subhalos are predicted to be largely abundant inside larger halos, i.e., galaxies like ours, and are thought to form first and later merge to form larger structures. Dwarf satellite galaxies -- the most massive exponents of halo substructure in our own galaxy -- are already known to be excellent targets and, indeed, they are constantly scrutinized by current gamma-ray experiments in their search for DM annihilation signals. Lighter subhalos not massive enough to have a visible baryonic counterpart may be good targets as well given their typical number densities and distances. In addition, the clumpy distribution of subhalos residing in larger halos may boost the DM signals considerably. In an era in which gamma-ray experiments possess, for the first time, the exciting potential of reaching the most relevant regions of the DM parameter space, a profound knowledge of the DM targets and scenarios being tested at present is mandatory if we aim for accurate predictions of DM-induced fluxes, for investing significant telescope observing time to selected targets, and for deriving robust conclusions from our DM search efforts. In this regard, a precise characterization of the statistical and structural properties of subhalos becomes critical. With the Special Issue "The Role of Halo Substructure in Gamma-Ray Dark Matter Searches" [https://www.mdpi.com/journal/galaxies/special_issues/Gamma-RayDMS], we aimed to summarize where we stand today on our knowledge of the different aspects of the DM halo substructure; to identify what are the remaining big questions, how we could address these and, by doing so, to find new avenues for research.