Inner caustics of cold dark matter halos

Journal Article · Sun Jan 15 04:00:00 EST 2006 · Physical Review. D, Particles Fields

DOI:https://doi.org/10.1103/PHYSREVD.73.0· OSTI ID:20795702

Natarajan, Aravind ^[1]; Sikivie, Pierre ^[2]

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1. Institute for Fundamental Theory, Department of Physics, University of Florida, Gainesville, Florida 32611-8440 (United States)
2. School of Natural Sciences, Institute for Advanced Study, Princeton, New Jersey 08540 (United States)

We prove that a flow of cold collisionless particles from all directions in and out of a region necessarily forms a caustic. A corollary is that, in cold dark matter cosmology, galactic halos have inner caustics in addition to the more obvious outer caustics. The outer caustics are fold catastrophes located on topological spheres surrounding the galaxy. To obtain the catastrophe structure of the inner caustics, we simulate the infall of cold collisionless particles in a fixed gravitational potential. The structure of inner caustics depends on the angular momentum distribution of the infalling particles. We confirm a previous result that the inner caustic is a 'tricusp ring' when the initial velocity field is dominated by net overall rotation. A tricusp ring is a closed tube whose cross section is a section of an elliptic umbilic catastrophe. However, tidal torque theory predicts that the initial velocity field is irrotational. For irrotational initial velocity fields, we find the inner caustic to have a tentlike structure which we describe in detail in terms of the known catastrophes. We also show how the tent caustic transforms into a tricusp ring when a rotational component is added to the initial velocity field.

• OSTI ID: 20795702
• Journal Information: Physical Review. D, Particles Fields, Journal Name: Physical Review. D, Particles Fields Journal Issue: 2 Vol. 73; ISSN PRVDAQ; ISSN 0556-2821
• Country of Publication: United States
• Language: English

Related Subjects

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS
ANGULAR MOMENTUM
COSMOLOGY
DISTRIBUTION
GALAXIES
NONLUMINOUS MATTER
POTENTIALS
ROTATION
TOPOLOGY
VELOCITY