The Spur and the Gap in GD-1: Dynamical Evidence for a Dark Substructure in the Milky Way Halo

By A. Bonaca, David W. Hogg, Adrian M. Price-Whelan, C. Conroy. Astrophysical Journal, 2018

175 citations recorded by the source corpus.

We present a model for the interaction of the GD-1 stellar stream with a massive perturber that naturally explains many of the observed stream features, including a gap and an off-stream spur of stars. The model involves an impulse by a fast encounter, after which the stream grows a loop of stars at different orbital energies. At specific viewing angles, this loop appears offset from the stream track. A quantitative comparison of the spur-and-gap features prefers models where the perturber is in the mass range of 106–108 M⊙. Orbit integrations back in time show that the stream encounter could not have been caused by any known globular cluster or dwarf galaxy with a determined orbit, and mass, size, and impact parameter arguments show that it could not have been caused by a molecular cloud in the Milky Way disk. The most plausible explanation for the gap-and-spur structure is an encounter with a dark matter substructure, like those predicted to populate galactic halos in ΛCDM cosmology. However, the expected densities of ΛCDM subhalos in this mass range and in this part of the Milky Way are 2σ–3σ lower than the inferred density of the GD-1 perturber. This observation opens up the possibility that detailed observations of streams could measure the mass spectrum of dark matter substructures and even identify individual substructures and their orbits in the Galactic halo.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/2c3f36208a5e40c00107d262e7da3717c784a15f

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Citations in the corpus

Constraints on Dark Matter Microphysics from the Milky Way Satellite Population (2019, methodology): “For example, upcoming imaging surveys such as LSST will facilitate systematic searches for density gaps in Galactic stellar streams, which potentially trace even lower-mass subhalos than those inferred from satellites (e.g., Bonaca et al. 2018).”
The total mass of the Large Magellanic Cloud from its perturbation on the Orphan stream (2018, background): “For fast encounters with dense objects, this can eject stars from the stream and lead to spur-like features (e.g. Bonaca et al. 2018).”
Mining for Dark Matter Substructure: Inferring Subhalo Population Properties from Strong Lenses with Machine Learning (2019, methodology): “…the kinematic phase-space distribution in cold stellar streams (Johnston et al. 1999; Carlberg 2012; Carlberg & Grillmair 2013; Bonaca & Hogg 2018; Bonaca et al. 2019), and in Galactic stellar ﬁelds (Buschmann et al. 2018) have been proposed as methods to look for low-mass subhalos through their…”