The time evolution of gaps in tidal streams

Abstract

We model the time evolution of gaps in tidal streams caused by the impact of a dark matter subhalo, while both orbit a spherical gravitational potential. To this end, we make use of the simple behaviour of orbits in action-angle space. A gap effectively results from the divergence of two nearby orbits whose initial phase-space separation is, for very cold thin streams, largely given by the impulse induced by the subhalo. We find that in a spherical potential the size of a gap increases linearly with time for sufficiently long timescales. We have derived an analytic expression that shows how the growth rate depends on the mass of the perturbing subhalo, its scale and its relative velocity with respect to the stream. We have verified these scalings using N-body simulations and find excellent agreement. For example, a subhalo of mass 10^8 Msun directly impacting a very cold thin stream on an inclined orbit can induce a gap that may reach a size of several tens of kpc after a few Gyr. The gap size fluctuates importantly with phase on the orbit, and it is largest close to pericentre. This indicates that it may not be fully straightforward to invert the spectrum of gaps present in a stream to recover the mass spectrum of the subhalos.

4 pages, 4 figures, ApJ Letters in press

References in corpus (7)

• Inference of the Cold Dark Matter substructure mass function at z=0.2 using strong gravitational lenses
• The number and size of subhalo-induced gaps in stellar streams
• Forensics of Subhalo-Stream Encounters: The Three Phases of Gap Growth
• Properties of Dark Subhaloes from Gaps in Tidal Streams
• Dynamics of stream-subhalo interactions
• Star Streams in Triaxial Isochrone Potentials with Sub-Halos
• Miller's instability, microchaos and the short-term evolution of initially nearby orbits

Cited by in corpus (7)

• The Southern Stellar Stream Spectroscopic Survey ($S^5$): Overview, Target Selection, Data Reduction, Validation, and Early Science
• Orbits of massive satellite galaxies: II. Bayesian Estimates of the Milky Way and Andromeda masses using high precision astrometry and cosmological simulations
• The Density Structure of Simulated Stellar Streams
• Time evolution of gaps in stellar streams in axisymmetric Stäckel potentials
• Gaps in stellar streams as a result of globular cluster fly-bys
• Stream-subhalo interactions in the Aquarius simulations
• Segue 2 Recently Collided with the Cetus-Palca Stream: New Opportunities to Constrain Dark Matter in an Ultra-Faint Dwarf