Advancing Stellar Streams as a Dark Matter Probe -- I: Evolution of the CDM subhalo population

TL;DR

This paper develops a detailed, physically motivated model for the interaction of dark matter subhalos with stellar streams, predicting more gaps than previous models and enhancing the use of streams as dark matter probes.

Contribution

It introduces a time-dependent, physically calibrated model for subhalo populations affecting stellar streams, improving gap statistics predictions over prior simplified models.

Findings

Predicts 20% more gaps in streams than previous models.

Deep gaps are up to 60% more frequent with the new model.

Provides a more accurate framework for using stellar streams to probe dark matter.

Abstract

Stellar streams, long, thin streams of stars, have been used as sensitive probes of dark matter substructure for over two decades. Gravitational interactions between dark matter substructures and streams lead to the formation of low-density ``gaps'' in streams, with any given stream typically containing no more than a few such gaps. Prior models for the statistics of such gaps have relied on several simplifying assumptions for the properties of the subhalo population in the cold dark matter scenario. With the expected forthcoming increase in the number of streams and gaps observed, this work develops a more detailed model for the statistics of subhalos interacting with streams and tests some of the assumptions made in prior works. Instead of using simple fits to N-body estimates of subhalo population statistics at $z=0$ as in previous work, we make use of realizations of time-dependent subhalo populations generated from an entirely physical model, incorporating structure formation and subhalo orbital evolution, including tidal heating and stripping physics, which has been carefully calibrated to match results of cosmological N-body simulations. We find that this model predicts 20% more gaps (up to 60% for deep gaps) on average in Pal-5-like streams than prior works.