An attractor for dark matter structures

TY - JOUR

T1 - An attractor for dark matter structures

AU - Hansen, Steen Harle

AU - Juncher, Diana

AU - Sparre, Martin

PY - 2010/8/1

Y1 - 2010/8/1

N2 - Cosmological simulations of dark matter (DM) structures have identified a set of universal profiles, and similar characteristics have been seen in non-cosmological simulations. There has therefore been speculation as to whether these profiles of collisionless systems relate to accretion and merger history, or if there is an attractor for the DM systems. Here, we identify such a one-dimensional attractor in the three-dimensional space spanned by the two radial slopes of the density and velocity dispersion, and the velocity anisotropy. This attractor effectively removes 1 degree of freedom from the Jeans equation. It also allows us to speculate on a new fluid interpretation for the Jeans equation, with an effective polytropic index for the DM particles between 1/2 and 3/4. If this attractor solution holds for other collisionless structures, then it may hold the key to breaking the massanisotropy degeneracy, which presently prevents us from uniquely measuring the mass profiles in dwarf galaxies.

AB - Cosmological simulations of dark matter (DM) structures have identified a set of universal profiles, and similar characteristics have been seen in non-cosmological simulations. There has therefore been speculation as to whether these profiles of collisionless systems relate to accretion and merger history, or if there is an attractor for the DM systems. Here, we identify such a one-dimensional attractor in the three-dimensional space spanned by the two radial slopes of the density and velocity dispersion, and the velocity anisotropy. This attractor effectively removes 1 degree of freedom from the Jeans equation. It also allows us to speculate on a new fluid interpretation for the Jeans equation, with an effective polytropic index for the DM particles between 1/2 and 3/4. If this attractor solution holds for other collisionless structures, then it may hold the key to breaking the massanisotropy degeneracy, which presently prevents us from uniquely measuring the mass profiles in dwarf galaxies.

U2 - 10.1088/2041-8205/718/2/L68

DO - 10.1088/2041-8205/718/2/L68

M3 - Journal article

SN - 0004-637X

VL - 718

SP - L68-L72

JO - Astrophysical Journal Letters

JF - Astrophysical Journal Letters

IS - 2

ER -