C-19 and Hot, Wide, Star Streams

TL;DR

This paper explains the unusual properties of the C-19 star stream as a result of tidal dissolution of a globular cluster in a Milky Way-like galaxy with a CDM halo and subhalos, supported by cosmological simulations.

Contribution

It demonstrates that a hot, wide star stream like C-19 can originate from a globular cluster disrupted in a CDM halo with subhalos, using cosmological simulations and modeling.

Findings

C-19's velocity dispersion and width are consistent with a disrupted globular cluster.

A model with a ~2x10^4 M_sun progenitor in a Milky Way-like halo reproduces observed properties.

The stream's characteristics are explained by tidal disruption in a CDM halo with subhalos.

Abstract

The C-19 star stream has the abundance characteristics of an unusually metal poor globular cluster but kinematically is uncharacteristically hot and wide for a cluster stream, having a line of sight velocity dispersion of 7 +/- 2 km/s and a 1-sigma width of 240 pc. We show that the tidal dissolution of an old, lower mass, globular cluster in a CDM galactic halo can create a hot, wide stream currently near orbital apocenter. A cosmological Milky Way n-body simulation motivates the parameters for an evolving Milky Way halo potential containing an orbiting subhalo population in which we model a star cluster progenitor of C-19. The same model parameters have been used for a GD-1 stream model. The ~7 km/s velocity dispersion is readily accomplished with an evolving CDM subhalo population, a progenitor cluster mass ~2x10^4 M_sun and an orbit that keeps the progenitor orbital pericenter within about 10 kpc of the Milky Way dark halo or its precursors.