Testing the Dark Matter Caustic Theory Against Observations in the Milky Way

Abstract

We test a particular theory of dark matter in which dark matter axions form ring "caustics" in the plane of the Milky Way against actual observations of Milky Way stars. According to this theory, cold, collisionless dark matter particles with angular momentum flow in and out of the Milky Way on sheets. These flows form caustic rings (at the positions of the rings, the density of the flow is formally infinite) at the locations of closest approach to the Galactic center. We show that the caustic ring dark matter theory reproduces a roughly logarithmic halo, with large perturbations near the rings. We show that the theory can reasonably match the observed rotation curve of the Milky Way. We explore the effects of the caustic rings on dwarf galaxy tidal disruption using N-body simulations. In particular, simulations of the Sagittarius dwarf galaxy tidal disruption in a caustic ring halo potential match observations of the trailing tidal tail as far as 90 kpc from the Galactic center; they do not, however, match the leading tidal tail. None of the caustic ring, NFW, or triaxial logarithmic halos fit all of the data. The source code for calculating the acceleration due to a caustic ring halo has been made publicly available in the NEMO Stellar Dynamics Toolbox and the Milkyway@home client repository.

35 pages, 11 figures. To be published in The Astrophysical Journal

References in corpus (7)

• The Milky Way's Circular Velocity Curve to 60 kpc and an Estimate of the Dark Matter Halo Mass from Kinematics of ~2400 SDSS Blue Horizontal Branch Stars
• The formation of disc galaxies in high resolution moving-mesh cosmological simulations
• Rings and Radial Waves in the Disk of the Milky Way
• On the Shoulders of Giants: Properties of the Stellar Halo and the Milky Way Mass Distribution
• The Caustic Ring Model of the Milky Way Halo
• An Orbit Fit for the Grillmair Dionatos Cold Stellar Stream
• Maximum Likelihood Fitting of Tidal Streams With Application to the Sagittarius Dwarf Tidal Tails

Cited by in corpus (7)

• Gravitational probes of dark matter physics
• Dark matters on the scale of galaxies
• Updating the MACHO fraction of the Milky Way dark halo with improved mass models
• Preparing for low surface brightness science with the Vera C. Rubin Observatory: characterisation of tidal features from mock images
• New astrophysical bounds on ultralight axionlike particles
• An Orbit Fit to Likely Hermus Stream Stars
• Testing universal dark-matter caustic rings with galactic rotation curves