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Article Dans Une Revue International Journal of Modern Physics A Année : 2011

Constant Surface Gravity and Density Profile of Dark Matter

Résumé

Cumulative observational evidence confirms that the surface gravity of dark matter (DM) halos mu0 D = r0rho0, where r0 and rho0 are the halo core radius and central density, respectively, is nearly constant and independent of galaxy luminosity for a high number of galactic systems (spirals, dwarf irregular and spheroidals, elliptics) spanning over 14 magnitudes in luminosity and of different Hubble types. Remarkably, its numerical value, mu0D ~=140M&sun;/pc2 = (18.6 MeV)3, is approximately the same (up to a factor of 2) in all these systems. First, we present the physical consequences of the independence of mu0D from r0: the energy scales as the volume ˜ r03, while the mass and the entropy scale as the surface ˜ r02 and the surface times log r0, respectively. Namely, the entropy scales similarly to the black hole entropy but with a much smaller coefficient. Second, we compute the surface gravity and the density profile for small scales from first principles and the evolution of primordial density fluctuations from the end of inflation till today using the linearized Boltzmann-Vlasov equation. The density profile rholin(r) obtained in this way decreases as r-1-ns/2 for intermediate scales, where ns~=0.964 is the primordial spectral index. This scaling is in remarkable agreement with the empirical behavior found observationally and in N-body simulations: r-1.6±0.4. The observed value of mu0D indicates that the DM particle mass m is on the keV scale. The theoretically derived density profiles rholin(r) turn to be cored for m on the keV scale and they are cusped for m on the GeV scale or beyond. We consider both fermions and bosons as DM particles decoupling either ultrarelativistically or nonrelativistically. Our results do not use any particle physics model and vary slightly with the statistics of the DM particle.

Dates et versions

hal-03742217 , version 1 (02-08-2022)

Identifiants

Citer

Hector J. de Vega, Norma G. Sánchez. Constant Surface Gravity and Density Profile of Dark Matter. International Journal of Modern Physics A, 2011, 26, pp.1057-1072. ⟨10.1142/S0217751X11051299⟩. ⟨hal-03742217⟩
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