Characterization of subhalo structural properties and implications for dark matter annihilation signals

Abstract

A prediction of the standard ΛCDM cosmological model, also confirmed by N-body simulations, is that dark matter (DM) halos are teeming with numerous self-bound substructure, or subhalos. The precise properties of these subhalos represent important probes of the underlying cosmological model. In this work, we use data from the N-body Via Lactea II and ELVIS Milky Way-size simulations to learn about the structure of subhalos with masses 10 6 − 10 11 h −1 M . Thanks to a superb subhalo statistics, by taking a profileindependent approach, we study subhalo properties as a function of the distance to the host halo center and subhalo mass, and provide a set of fits that, including both dependences, accurately describe the subhalo structure. With this at hand, we also investigate the role of subhalos on the search for DM via its annihilation products. Indeed, previous work has shown that subhalos are expected to boost the DM signal of their host halos significantly. Yet, these works have traditionally assumed that subhalos exhibit similar structural properties than those of field halos of the same mass, while it is well known from simulations that subhalos are more concentrated. Building upon the results from our N-body data analysis, we refine the substructure boost model of Sánchez-Conde & Prada (2014). We find boost values that are a factor 2 − 3 higher than previous ones. We further refine our boost model to include unavoidable tidal stripping effects on the subhalo population. For field halos, this only introduces a moderate (∼ 20% − 30%) suppression of the boost. Yet, for subhalos like those hosting the dwarf satellite galaxies of the Milky Way, tidal stripping does play a critical role, the total boost for these objects being only at the level of a few tens of percent in the most optimistic cases. Finally, we provide a parametrization of the boost factor for field halos that can be safely applied over a wide halo mass range.

3fgl Demographics Outside the Galactic Plane Using Supervised Machine Learning: Pulsar and Dark Matter Subhalo Interpretations

“…Note that these limits would only be slightly better if one includes the role of halo substructure to boost the subhalo annihilation flux (Moliné et al 2016;Sánchez-Conde & Prada 2014). More precisely, following Moliné et al (2016), we estimate at most a factor ∼10% stronger limits when boosting the annihilation signal in the mass range 10 4 -10 7 M e .…”

“…Note that these limits would only be slightly better if one includes the role of halo substructure to boost the subhalo annihilation flux (Moliné et al 2016;Sánchez-Conde & Prada 2014). More precisely, following Moliné et al (2016), we estimate at most a factor ∼10% stronger limits when boosting the annihilation signal in the mass range 10 4 -10 7 M e . For comparison, we also show constraints if eventually no dark matter subhalos turn up in the 3FGL from the Aquarius (Bertoni et al 2015) and Via Lactea II simulations (Schoonenberg et al 2016), respectively.…”

Constraining annihilating dark matter by radio data of M33

“…These substructures can greatly increase the annihilation rate to about an order of magnitude [31,32]. The boost factor B f can describe how substructures affect the total annihilation rate [31,33]. Recent simulations indicate that the boost factor can be simply obtained by the following empirical formula [33]:…”

“…The boost factor B f can describe how substructures affect the total annihilation rate [31,33]. Recent simulations indicate that the boost factor can be simply obtained by the following empirical formula [33]:…”

Mapping the Tidal Destruction of the Hercules Dwarf: A Wide-field DECam Imaging Search for RR Lyrae Stars

“…UFDs are also strong targets for the observation of predicted γ-ray flux from annihilation of dark matter particle candidates because of their high mass-to-light ratios (e.g., Strigari et al 2007;Bonnivard et al 2015a;Drlica-Wagner et al 2015;Ruchayskiy et al 2016;Moliné et al 2017).…”