Modeling Globular Cluster Stellar Streams with a Basis-Expansion N-body Code

TL;DR

This paper introduces KRIOS, a basis-expansion N-body code that accurately models globular cluster stellar streams more efficiently than traditional methods, improving understanding of galaxy formation and dark matter distribution.

Contribution

KRIOS provides a new, efficient, and accurate approach to modeling stellar streams, bridging the gap between particle-spray and direct N-body simulations.

Findings

KRIOS reproduces NBODY6++GPU models more accurately than particle spray.

KRIOS is faster than direct N-body simulations for realistic systems.

Stream morphology and kinematics vary with progenitor binding strength.

Abstract

Globular cluster stellar streams probe galaxy-formation processes and can potentially reveal the distribution of dark matter in galaxies. In many theoretical studies, streams are modeled with particle-spray or direct N-body codes. But particle-spray methods abstract away the internal dynamics of the progenitor by making strong assumptions about the escape physics, while direct N-body is prohibitively expensive for realistic (N>10^5) systems. In this paper, we present the stream-modeling capabilities of KRIOS, a new basis-expansion N-body code for collisional stellar dynamics, that bridges this runtime vs. accuracy gap. We show that KRIOS reproduces NBODY6++GPU cluster models, and their associated streams, more accurately than particle spray in a fraction of the NBODY6++GPU wall-clock time. We then compare KRIOS to various particle-spray methods on 10 orbits similar to known Milky Way streams. The morphology and kinematics of these streams most disagree when the progenitor is tightly bound to the host, as these systems are often subject to stronger tidal forces. Finally, we discuss which elements of the progenitor physics are most important for modeling stellar streams and how these might be incorporated into particle-spray methods.