Formation and Evolution of Self-Interacting Dark Matter Haloes
نویسندگان
چکیده
We have derived the first, fully-cosmological, similarity solutions for cold dark matter (CDM) halo formation in the presence of nongravitational collisionality (i.e. elastic scattering), which provides an analytical theory of the effect of the self-interacting dark matter (SIDM) hypothesis on halo density profiles. Collisions transport heat inward which flattens the central cusp of the CDM density profile to produce a constantdensity core, while continuous infall pumps energy into the halo to stabilize the core against gravothermal catastrophe. This is contrary to previous analyses based upon isolated haloes, which predict core collapse within a Hubble time. These solutions improve upon earlier attempts to model the formation and evolution of SIDM haloes, offer deeper insight than existing N-body experiments, and yield a more precise determination of the dependence of halo density profile on the value of the CDM self-interaction cross section. Different solutions arise for different values of the dimensionless collisionality parameter Q ≡ σρbrvir ∝ rvir/λmfp, where σ is the scattering cross section per unit mass, ρb is the cosmic mean matter density, rvir is halo virial radius and λmfp is the collision mean free path. The maximum flattening of central density occurs for an intermediate value of Q, Qth, at which the halo is maximally relaxed to isothermality. The density profiles with constant-density cores preferred by dwarf and low surface brightness galaxy (LSB) rotation curves are best fit by the maximally-flattened (Q = Qth) solution. If we assume that dwarfs and LSB galaxies formed at their typical collapse epoch in ΛCDM, then the value of σ which makesQ = Qth is σ ≃ 200 cm 2 g, much higher than previous estimates, σ ≃ [0.5− 5] cm g, based on N-body experiments. If σ is independent of collision velocity, then the same value σ ≃ 200 cm g would make Q > Qth for clusters, which typically formed only recently, resulting in relatively less flattening of their central density profile and a smaller core.
منابع مشابه
The formation of compact massive self-gravitating discs in metal-free haloes with virial temperatures of ∼ 13000-30000K
We have used the hydrodynamical AMR code ENZO to investigate the dynamical evolution of the gas at the centre of dark matter haloes with virial velocities of ∼ 20−30 km s and virial temperatures of ∼ 13000−30000K at z ∼ 15 in a cosmological context. The virial temperature of the dark matter haloes is above the threshold where atomic cooling by hydrogen allows the gas to cool and collapse. We ne...
متن کاملCosmological Evolution of Supergiant Star-Forming Clouds
In an exploration of the birthplaces of globular clusters, we present a careful examination of the formation of self-gravitating gas clouds within assembling dark matter haloes in a hierarchical cosmological model. Our high-resolution smoothed particle hydrodynamical simulations are designed to determine whether or not hypothesized supergiant molecular clouds (SGMCs) form and, if they do, to de...
متن کاملEvolution of Dark-matter Haloes in a Variety of Dark-energy Cosmologies
High-resolution, numerical simulations of 17 cluster-sized dark-matter haloes in eight different cosmologies with and without dynamical dark energy confirm the picture that core halo densities are imprinted early during their formation by the mean cosmological density. Quite independent of cosmology, halo concentrations have a log-normal distribution with a scatter of ∼ 0.2 about the mean. We p...
متن کاملar X iv : a st ro - p h / 06 11 20 5 v 1 7 N ov 2 00 6 Self - consistent models of cuspy triaxial galaxies with dark matter haloes
We have constructed realistic, self-consistent models of triaxial elliptical galaxies embedded in triaxial dark matter haloes. We examined three different models for the shape of the dark matter halo: (i) the same axis ratios as the luminous matter (0.7:0.86:1); (ii) a more prolate shape (0.5:0.66:1); (iii) a more oblate shape (0.7:0.93:1). The models were obtained by means of the standard orbi...
متن کاملDark Matter Halo Mergers and Quasars
DARK MATTER HALO MERGERS AND QUASARS Jorge Moreno Ravi Sheth, Advisor The formation and evolution of galaxies and the supermassive black holes they harbor at their nuclei depends strongly on the merger history of their surrounding dark matter haloes. First we developed a semi-analytic algorithm that describes the merger history tree of a halo. The following tests were performed: the conditional...
متن کامل