Particle tagging and its implications for stellar population dynamics

TL;DR

This paper compares particle tagging methods with hydrodynamical simulations to understand stellar halo properties, emphasizing the importance of phase-space diffusion and live tagging schemes for accurate results.

Contribution

It demonstrates conditions where particle tagging accurately reproduces stellar density profiles and highlights the significance of phase-space diffusion in modeling stellar halos.

Findings

Particle tagging can match hydrodynamical stellar density profiles under certain conditions.

Phase-space diffusion significantly influences the final stellar halo structure.

Live tagging schemes improve the accuracy of particle tagging methods.

Abstract

We establish a controlled comparison between the properties of galactic stellar halos obtained with hydrodynamical simulations and with `particle tagging'. Tagging is a fast way to obtain stellar population dynamics: instead of tracking gas and star formation, it `paints' stars directly onto a suitably defined subset of dark matter particles in a collisionless, dark-matter-only simulation.Our study shows that there are conditions under which particle tagging generates good fits to the hydrodynamical stellar density profiles of a central Milky-Way-like galaxy and its most prominent substructure. Phase-space diffusion processes are crucial to reshaping the distribution of stars in infalling spheroidal systems and hence the final stellar halo. We conclude that the success of any particular tagging scheme hinges on this diffusion being taken into account, at a minimum by making use of `live' tagging schemes, in which particles are regularly tagged throughout the evolution of a galaxy.