Properties of Dark Subhaloes from Gaps in Tidal Streams

TL;DR

This paper demonstrates how the properties of dark matter subhaloes, such as mass and size, can be inferred from the gaps they create in tidal streams, aiding in understanding dark matter distribution.

Contribution

First, it shows how to reliably determine subhalo properties from stream gaps, including phase-space data, across various observational setups.

Findings

Subhalo properties can be inferred from stream gaps with high accuracy.

Mass and size degeneracies can be constrained, especially for M>10^7 M_.

Method is applicable to data from SDSS, DES, Gaia, and LSST.

Abstract

Cold or Warm, the Dark Matter substructure spectrum must extend to objects with masses as low as $10^7 M_\odot$, according to the most recent Lyman-$\alpha$ measurements. Around a Milky Way-like galaxy, more than a thousand of these subhaloes will not be able to form stars but are dense enough to survive even deep down in the potential well of their host. There, within the stellar halo, these dark pellets will bombard tidal streams as they travel around the Galaxy, causing small but recognizable damage to the stream density distribution. The detection and characterization of these stream ruptures will allow us to constrain the details of the subhalo-stream interaction. In this work, for the first time, we will demonstrate how the properties of a subhalo, most importantly its mass and size, can be reliably inferred from the gap it produces in a tidal stream. For a range of realistic observational setups, mimicking e.g. SDSS, DES, Gaia and LSST data, we find that it is possible to measure the {\it complete set} of properties (including the phase-space coordinates during the flyby) of dark perturbers with $M>10^7 M_\odot$, up to a 1d degeneracy between the mass and velocity.