The tidal evolution of dark matter substructure -- I. Subhalo density profiles

Abstract

Accurately predicting the abundance and structural evolution of dark matter subhaloes is crucial for understanding galaxy formation, modeling galaxy clustering, and constraining the nature of dark matter. Due to the nonlinear nature of subhalo evolution, cosmological $N$-body simulations remain its primary method of investigation. However, it has recently been demonstrated that such simulations are still heavily impacted by artificial disruption, diminishing the information content on small scales and reducing the reliability of all simulation-calibrated semi-analytical models. In this paper, we utilize the recently released DASH library of high-resolution, idealized simulations of the tidal evolution of subhaloes, which are unhindered by numerical overmerging due to discreteness noise or force softening, to calibrate an improved, more-accurate model of the evolution of the density profiles of subhaloes that undergo tidal heating and stripping within their host halo. By testing previous findings that the structural evolution of a tidally truncated subhalo depends solely on the fraction of mass stripped, independent of the details of the stripping, we identify an additional dependence on the initial subhalo concentration. We provide significantly improved fitting functions for the subhalo density profiles and structural parameters ($V_{\max }$ and $r_{\max }$) that are unimpeded by numerical systematics and applicable to a wide range of parameter space. This model will be an integral component of a future semi-analytical treatment of substructure evolution, which can be used to predict key quantities, such as the evolved subhalo mass function and annihilation boost factors, and validate such calculations performed with cosmological simulations.

11 pages, 6 figures, 2 tables. Accepted to MNRAS

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• Shedding light on low-mass subhalo survival and annihilation luminosity with numerical simulations
• The Milky Way, Coming into Focus: Precision Astrometry Probes its Evolution, and its Dark Matter
• Boosting small-scale structure via primordial black holes and implications for sub-GeV dark matter annihilation
• An Accurate Comprehensive Approach to Substructure: III. Masses and Formation Times of the Host Haloes
• A universal model for the evolution of tidally stripped systems
• An Accurate Comprehensive Approach to Substructure: II. Stripped Subhaloes
• Testing the key role of the stellar mass-halo mass relation in galaxy merger rates and morphologies via DECODE, a novel Discrete statistical sEmi-empiriCal mODEl