Detectability of dark matter subhalo impacts in Milky Way stellar streams

TL;DR

This paper presents a method to estimate the smallest dark matter subhalo mass detectable through impacts on Milky Way stellar streams, considering various observational scenarios and stream properties.

Contribution

It introduces an analytic approach to quickly assess the detectability of dark matter subhalos in different stellar streams, expanding analysis beyond the few well-studied cases.

Findings

Minimum detectable subhalo mass for GD-1 in Gaia data is ~6×10^6 M_sun.

LSST can detect subhalos as small as ~8×10^5 M_sun in 10 years.

Ranked streams by their sensitivity to dark matter subhalo impacts.

Abstract

Stellar streams are a promising way to probe the gravitational effects of low-mass dark matter (DM) subhalos. In recent years, there has been a remarkable explosion in the number of stellar streams detected in the Milky Way, and hundreds more may be discovered with future surveys such as LSST. Studies of DM subhalo impacts on streams have so far focused on a few of the thinnest and brightest streams, and it is not known how much information can be gained from the others. In this work, we develop a method to quickly estimate the minimum detectable DM subhalo mass of a given stream, depending on its width, length, distance, and stellar density. We use an analytic model for the impacts and apply a test statistic to determine whether they are detectable. We consider several observational scenarios, based on current and future surveys including Gaia, DESI, Via, and LSST. We find that at 95% confidence level, a stream like GD-1 has a minimum detectable subhalo mass of $\sim 6\times 10^6~\mathrm{M}_\odot$ in Gaia data and $\sim 8\times 10^5~\mathrm{M}_\odot$ with LSST 10 year sensitivity. Applying our results to confirmed Milky Way streams, we rank order them by their sensitivity to DM subhalos and identify promising ones for further study.