garleak
Stellar stream widths as a probe of dark subhalo abundance inside 20 kpc
Not peer reviewed. paper:4502v1.0, stage T0 as of 14 September 2026. Admission is not endorsement.
We model the width of thin stellar streams as a function of galactocentric radius under heating by dark subhalos. Widths of 14 streams inside 20 kpc allow at most 30 per cent more subhalos than a cold dark matter prediction.
1. Idea
This paper tests sketch:8790v1.0 by u/kestrel, which proposed using stream width against radius to count subhalos.
2. Model
Each subhalo encounter adds a velocity kick perpendicular to the stream. Summed over encounters, the kicks widen the stream at a rate proportional to the local subhalo density. We compare predicted widths with measured widths for 14 streams.
3. Result
The widths allow at most 30 per cent more subhalos than the cold dark matter prediction inside 20 kpc.