Does the second caustic ring of dark matter cause the Monoceros Ring of stars?

Abstract

Caustic rings of dark matter were predicted to exist in the plane of the Galaxy at radii a n ' 40 kpc=n for n 1; 2; 3; . . . . The recently discovered Monoceros Ring of stars is located near the n 2 caustic, prompting us to consider a possible connection between these two objects. We identify two processes through which the Monoceros Ring of stars may have formed. One process is the migration of gas to an angular velocity minimum at the caustic leading to enhanced star formation there. The other is the adiabatic deformation of star orbits as the caustic slowly grows in mass and radius. The second process predicts an order 100% enhancement of the density of disk stars at the location of the caustic ring.

A Megacam Survey of Outer Halo Satellites. Iv. Two Foreground Populations Possibly Associated With the Monoceros Substructure in the Direction of NGC 2419 and Koposov 2

“…Unfortunately, none of the existing arguments favoring or rejecting the extragalactic origin of the Monoceros Ring completely rule out the other hypotheses. Additional processes have been suggested to explain the detection of such a vast halo substructure, including the disk distortion generated by a close encounter (Younger et al 2008), the existence of caustic rings of dark matter in that position within the Galaxy (Natarajan & Sikivie 2007) and the accretion of the Sgr dwarf galaxy, which might have a direct impact on the formation of stellar rings in the outer halo (Michel-Dansac et al 2011;Purcell et al 2011).…”

Tidal Streams in the Local Group and Beyond

“…Another explanation for the origin of a ring at a radius of 20 kpc from the Galactic center is given in Natarajan and Sikivie (2007). This paper points out that Sikivie (1998) predicted a caustic ring of dark matter particles 20 kpc from the Galactic center, significantly before the Monoceros Ring was discovered.…”

“…Natarajan and Sikivie (2007) suggest that gas could migrate to the caustic and preferentially form stars at that distance, or alternatively that the caustic could deform the orbits of stars that have already formed so that they are preferentially found on the caustic. However, neither of these scenarios is likely to create a ring of stars that extends to heights 5 kpc above the Galactic plane, as is observed.…”

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

“…The caustic ring dark matter theory has been developed by Pierre Sikivie (Sikivie et al 1995;Sikivie 2003Sikivie , 2011Natarajan & Sikivie 2007;Duffy & Sikivie 2008;Banik & Sikivie 2013) over the past 20 years. Although Sikivie started from the spherically symmetric self-similar models of Fillmore & Goldreich (1984) and Bertschinger (1985), it is important to note that the Sikivie model has evolved to include the physics of dark matter particles beyond a simple gravitational interaction.…”

“…There is one equation for the density at a position near a caustic ring and another for the density at a position far away from a caustic ring. The equation for the density near a caustic ring is given by Equation (2) in Natarajan & Sikivie (2007): Natarajan & Sikivie (2007). Here, α is an angle associated with the particleʼs last turnaround, and τ is the time when the particle crosses the z = 0 plane.…”