Open AccessEvolution of the phase‐space density of dark matter haloes and mixing effects in merger events
Author(s) -
Peirani Sébastien,
Durier Fabrice,
De Freitas Pacheco José A.
Publication year - 2006
Publication title -
monthly notices of the royal astronomical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.058
H-Index - 383
eISSN - 1365-2966
pISSN - 0035-8711
DOI - 10.1111/j.1365-2966.2006.10149.x
Subject(s) - physics , halo , dark matter , astrophysics , cold dark matter , mixing (physics) , velocity dispersion , sigma , phase (matter) , dispersion (optics) , dark matter halo , cosmology , galaxy , astronomy , quantum mechanics
Cosmological N ‐body simulations were performed to study the evolution of the phase‐space density Q =ρ/σ 3 of dark matter haloes. No significant differences in the scale relations Q ∝σ −2.1 or Q ∝ M −0.82 are seen for the ‘cold’ or ‘warm’ dark matter models. The follow‐up of individual haloes from z = 10 up to the present time indicate the existence of two main evolutionary phases: an early and fast one (10 > z > 6.5) , in which Q decreases on the average by a factor of 40 as a consequence of the randomization of bulk motions, and a late and long one (6.5 > z ≥ 0) , in which Q decreases by a factor of 20 because of mixing induced by merger events. The study of these haloes has also evidenced that rapid and positive variations of the velocity dispersion, induced by merger episodes, are related to a fast decrease of the phase‐space density Q .