DASH: a library of dynamical subhalo evolution

Abstract

The abundance and demographics of dark matter substructure is important for many areas in astrophysics and cosmological N-body simulations have been the primary tool used to investigate them. However, it has recently become clear that the simulations are subject to numerical artefacts, which hampers a proper treatment of the tidal evolution of subhaloes. Unfortunately, no analytical models that accurately describe subhalo evolution exist either. We therefore present a library of idealized, high resolution N-body simulations of the tidal evolution of individual subhaloes that can be used to calibrate semi-analytical models and to complement cosmological simulations. The simulations focus on minor mergers, i.e., the mass of the subhalo is much smaller than that of the host halo, such that the impact of dynamical friction is negligible. This setup allows the adoption of a fixed analytical potential for modelling the host halo. The dynamical evolution of subhaloes is followed with N-body computations. In the library, four parameters, two of which characterize the subhalo orbit with respect to the host halo, and the two concentrations of the host-and subhalo, are varied over the ranges encountered in cosmological simulations. We show several representative examples from the library that illustrate the evolution of the subhalo mass and velocity dispersion profiles. Additionally, we make publicly available a pre-trained nonparametric model of the subhalo mass evolution based on random forest regression. This model is able to interpolate the simulation data at the 0.1 dex level and provides efficient access to the data for further use in modelling †. (GO) † DASH simulation data and machine learning model are available at https://cosmo.oca.eu/dash.

Breaking a dark degeneracy: The gamma-ray signature of early matter domination

“…Density profile P (R) of a subhalo simulated by Ref [127]. after 7 Gyr of tidal evolution; the host, subhalo, and orbital properties are similar to those of the Milky Way-Draco system.…”

Accelerated orbital decay of supermassive black hole binaries in merging nuclear star clusters

“…The tidally stripped material thus exerts a net drag force onto the binary (e.g. Fujii et al 2006;Fellhauer & Lin 2007;van den Bosch & Ogiya 2018;Ogiya et al 2019).…”

Mass-loss in tidally stripped systems: the energy-based truncation method

“…More recently, Green & van den Bosch (2019), provided an updated version of the fits given in Hayashi et al (2003); in this work they used the DASH smulations (Ogiya et al 2019), which are a suite of idealized minor merger simulations between NFW haloes. The advantages of these simulations over those used in Hayashi et al (2003) are that they have been carefully calibrated against numerical effects, they have initial conditions constructed from the full theoretical DF, and they consider different satellite concentrations.…”

“…given by: In their recent paper, have provided an update to the empirical model proposed by Hayashi et al (2003). While they still only consider NFW profiles, they vastly improve the accuracy of the model by using the publically available DASH simulations (Ogiya et al 2019). This library of simulations are carefully initialized by sampling the DF (rather than the Maxwellian approximation used in Hayashi et al (2003)).…”

“…Tidal stripping in minor mergers, for instance, is frequently studied using N -body simulations of a satellite halo evolving within a static host halo (e.g. Hayashi et al 2003;Kazantzidis et al 2004;Boylan-Kolchin & Ma 2007;Kampakoglou & Benson 2007;Peñarrubia et al 2008aPeñarrubia et al ,b, 2009Choi et al 2009;Peñarrubia et al 2010;Drakos et al 2017;Ogiya et al 2019;Delos 2019a). These idealized simulations provide a way to test the physical processes that govern subhalo evolution and determine the long-term fate of subhaloes as they lose mass, but they normally require interpretation with analytic models in order to extrapolate the results to the full range of situations relevant in calculations of annihilation rates, substructure lensing and semi-analytic models of galaxy evolution.…”