# Quantifying tidal stream disruption in a simulated Milky Way

## TL;DR

This study uses simulations of Milky Way-like halos to evaluate how different measures of tidal stream disruption can reveal the presence of dark matter substructure, emphasizing the importance of stream morphology over gap counting.

## Contribution

It introduces and compares multiple disruption measures, identifying stream thinness, tail symmetry, and path regularity as effective indicators of halo substructure.

## Key findings

- Stream gaps are unreliable indicators of halo substructure.
- Stream thinness, tail symmetry, and path regularity effectively distinguish halo potentials.
- Low-eccentricity, distant globular cluster streams are most informative.

## Abstract

Simulations of tidal streams show that close encounters with dark matter subhalos induce density gaps and distortions in on-sky path along the streams. Accordingly, observing disrupted streams in the Galactic halo would substantiate the hypothesis that dark matter substructure exists there, while in contrast, observing collimated streams with smoothly varying density profiles would place strong upper limits on the number density and mass spectrum of subhalos. Here, we examine several measures of stream "disruption" and their power to distinguish between halo potentials with and without substructure and with different global shapes. We create and evolve a population of 1280 streams on a range of orbits in the Via Lactea II simulation of a Milky Way-like halo, replete with a full mass range of {\Lambda}CDM subhalos, and compare it to two control stream populations evolved in smooth spherical and smooth triaxial potentials, respectively. We find that the number of gaps observed in a stellar stream is a poor indicator of the halo potential, but that (i) the thinness of the stream on-sky, (ii) the symmetry of the leading and trailing tails, and (iii) the deviation of the tails from a low-order polynomial path on-sky ("path regularity") distinguish between the three potentials more effectively. We find that globular cluster streams on low-eccentricity orbits far from the galactic center (apocentric radius ~ 30-80 kpc) are most powerful in distinguishing between the three potentials. If they exist, such streams will shortly be discoverable and mapped in high dimensions with near-future photometric and spectroscopic surveys.