Tidal Evolution of Satellite Dwarf Galaxies. I. Tidal Tracks of Stellar Mass and Structure

Abstract

Satellite dwarf galaxies are reshaped by the tidal field of their host, a process that may account for part of the structural diversity of the observed dwarf population. We study how the stellar component of a satellite responds to tidal stripping using a suite of 480 controlled $N$-body simulations of satellite galaxies consisting of both dark matter (DM) and stars orbiting a Milky-Way-mass host. The simulated dwarfs span a broad range of DM halo structural and stellar-distribution parameters, including halo concentration, inner density slope, stellar-to-halo mass ratio, compactness of the stellar distribution with respect to the halo, as well as the Sérsic index of the stellar profiles. We present a comprehensive library of tidal tracks, namely, the evolution of the stellar mass, half-mass radius, mean surface density, and line-of-sight velocity dispersion, as functions of the bound mass fraction of the hosting DM subhalo, and provide simple and accurate fitting functions. We also identify the dependence of tidal tracks on key factors in the initial structural conditions. Notably, stellar compactness determines the duration over which the stellar mass remains relatively intact while the surrounding DM is being stripped. The Sérsic index and inner DM slope, in turn, govern the late-stage stellar mass-loss slope and the contraction or expansion of the remnant. Our simulations and empirical models provide a framework for modelling the stellar evolution of satellites across a broad range of progenitor structures, useful for semi-analytical models of satellite galaxy evolution.