Astronomy and Astrophysics – Astrophysics
Scientific paper
2004-10-07
Class.Quant.Grav.21:5275-5294,2004
Astronomy and Astrophysics
Astrophysics
13 pages, 3 eps figures, revtex 4. Accepted for publication in Classical and Quantum Gravity
Scientific paper
10.1088/0264-9381/21/22/018
In order to study their interplay with large scale cosmic evolution and with relativistic effects, such as gravitational lenses, quintessence sources or gravitational waves, we construct a post-Newtonian fluid framework for the "Navarro-Frenk-White'' (NFW) models of galactic halos that follow from N-body numerical simulations. Since these simulations are unable to resolve regions very near the halo center, the extrapolation of the fitting formula leads to a spherically averaged "universal'' density profile that diverges at the origin. We remove this inconvenient feature by replacing a small central region of the NFW halo with an interior Schwarzschild solution with constant density, continuously matched to the remaining NFW spacetime. A model of a single halo, as an isolated object with finite mass, follows by smoothly matching the NFW spacetime to a Schwarzschild vacuum exterior along the virial radius, the physical "cut-off'' customarily imposed, as the mass associated with NFW profiles diverges asymptotically. Numerical simulations assume weakly interacting collisionless particles, hence we suggest that NFW halos approximately satisfy an "ideal gas'' type of equation of state, where mass-density is the dominant rest--mass contribution to matter--energy, with the internal energy contribution associated with an anisotropic kinetic pressure. We show that, outside the central core, this pressure and the mass density roughly satisfy a polytropic relation. Since stellar polytropes are the equilibrium configurations in Tsallis' non-extensive formalism of Statistical Mechanics, we argue that NFW halos might provide a rough empirical estimate of the free parameter $q$ of Tsallis' formalism.
Matos Tonatiuh
Nunez Darío
Sussman Roberto A.
No associations
LandOfFree
A general relativistic approach to the Navarro-Frenk-White (NFW) galactic halos does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with A general relativistic approach to the Navarro-Frenk-White (NFW) galactic halos, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and A general relativistic approach to the Navarro-Frenk-White (NFW) galactic halos will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-315491