Forecasting the Population of Globular Cluster Streams in Milky Way-type Galaxies

TL;DR

This paper predicts the number, distribution, and properties of globular cluster streams in Milky Way-like galaxies, highlighting the potential for future surveys to enhance dark matter subhalo research.

Contribution

It introduces a hierarchical model to forecast globular cluster streams and assesses their detectability, revealing many streams are currently undetected and emphasizing future survey prospects.

Findings

Approximately 9000 globular clusters are fully phase-mixed in the galaxy center.

Around 1000 clusters survive as observable stellar streams.

Deep photometry can detect streams beyond 75 kpc, improving dark matter constraints.

Abstract

Thin stellar streams originating from globular clusters are among the most sensitive tracers of low-mass dark-matter subhalos. Joint analysis of the entire population of stellar streams will place the most robust constraints on the dark-matter subhalo mass function, and therefore the nature of dark matter. Here we use a hierarchical model of globular cluster formation to forecast the total number, masses and radial distribution of dissolved globular cluster in Milky Way-like galaxies. Furthermore, we generate mock stellar streams from these progenitors' orbital histories taking into account the clusters' formation and accretion time, mass, and metallicity. Out of $\sim$10,000 clusters more massive than $10^4$ M$_{\odot}$, $\sim$9000 dissolved in the central bulge and are fully phase-mixed at the present, while the remaining $\sim$1000 survive as coherent stellar streams. This suggests that the current census of $\sim$80 globular cluster streams in the Milky Way is severely incomplete. Beyond 15 kpc from the Galactic center we are missing hundreds of streams, of which the vast majority are from accreted GCs. Deep Rubin photometry $(g\lesssim27.5)$ would be able to detect these streams, even the most distant ones beyond $> 75$ kpc. We also find that M31 will have an abundance of streams at galactocentric radii of 30-100 kpc. We conclude that future surveys will find a multitude of stellar streams from globular clusters which can be used for dark matter subhalo searches.