NSF-ITP-93-122 A family of models for spherical stellar systems
نویسندگان
چکیده
We describe a one-parameter family of models of stable spherical stellar systems in which the phase-space distribution function depends only on energy. The models have similar density pro les in their outer parts ( / r 4 ) and central power-law density cusps, / r 3 , 0 < 3. The family contains the Ja e (1983) and Hernquist (1990) models as special cases. We evaluate the surface brightness pro le, the line-of-sight velocity dispersion pro le, and the distribution function, and discuss analogs of King's coretting formula for determining mass-to-light ratio. We also generalize the models to a two-parameter family, in which the galaxy contains a central black hole; the second parameter is the mass of the black hole. Our models can be used to estimate the detectability of central black holes and the velocity-dispersion pro les of galaxies that contain central cusps, with or without a central black hole.
منابع مشابه
NSF-ITP-95-154 gr-qc/95mmnnn Criticality and Bifurcation in the Gravitational Collapse of a Self-Coupled Scalar Field
We examine the gravitational collapse of a non-linear sigma model in spherical symmetry. There exists a family of continuously self-similar solutions parameterized by the coupling constant of the theory. These solutions are calculated together with the critical exponents for black hole formation of these collapse models. We also nd that the sequence of solutions exhibits a Hopf-type bifurcation...
متن کاملRelativistic Stellar Models with Quadratic Equation of State
In this paper, we have obtained and presented new relativistic stellar configurations considering an anisotropic fluid distribution with a charge distribution and a gravitational potential Z(x) that depends on an adjustable parameter. The quadratic equation of state based on Feroze and Siddiqui viewpoint is used for the matter distribution. The new solutions can be written in terms of elementar...
متن کاملCusped Spherical Stellar Systems with Anisotropic Velocities
Spherical models with constant velocity anisotropy β have distribution functions depending on binding energy E and angular momentum L of the form f (E, L) = L−2β fE(E). An inversion for the unknown function fE (E) is straightforward to derive and reduces to Eddington’s famous algorithm for isotropic models (β = 0). Importantly, if the anisotropy parameter of the model is a half-integer constant...
متن کاملProperties of Quasi-relaxed Stellar Systems in an External Tidal Field
In a previous paper, we have constructed a family of self-consistent triaxial models of quasi-relaxed stellar systems, shaped by the tidal field of the hosting galaxy, as an extension of the well-known spherical King models. For a given tidal field, the models are characterized by two physical scales (such as total mass and central velocity dispersion) and two dimensionless parameters (the conc...
متن کاملNSF-ITP-93-16 cond-mat/9301034 Lower Bound on the Energy Gap at Precise Locations
Recent inelastic-neutron-scattering measurements of a low-energy phonon in Bi 2 Sr 2 CaCu 2 O 8 provide enough information to place a lower bound on the energy gap magnitude at precise locations on the Fermi surface. Measurements of a few low-energy phonons should indicate whether the gap symmetry is d x 2 −y 2. Further measurements could map out the angle-resolved gap magnitude on the entire F...
متن کامل