2009/12/09 by A. Lapi, A. Paggi, A. Cavaliere +3
Physics and Astronomy · #Annihilation #Bulge #Center (category theory) #Cosmology and Gravitation Theories #Dark Matter and Cosmic Phenomena #Dark matter #Distribution (mathematics) #Galactic Center #Galaxies: Formation, Evolution, Phenomena #Galaxy #Gravitation #Velocity dispersion #astro-ph.CO #astro-ph.HE
paper · pdf · doi:10.1051/0004-6361/200913353
published as Astronomy and Astrophysics 510 (2010), 90 · 7 pages, 2 figures, uses aa.cls. Accepted by A&A
arxiv created 2009/12/09 · openalex publication_date 2009/12/21 · arxiv updated 2015/05/14 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
We discuss the <i>γ<i/>-ray signal to be expected from dark matter (DM) annihilations at the Galactic center. We describe the DM distribution in the Galactic halo, based on the Jeans equation for self-gravitating, anisotropic equilibria. In solving the Jeans equation, we adopted the specific correlation between the density and the velocity dispersion expressed by the powerlaw behavior of the DM “entropy” with <i>α<i/> <i>≈<i/> 1.25-1.3. Indicated (among others) by several recent <i>N<i/>-body simulations, this correlation is privileged by the form of the radial pressure term in the Jeans equation, and it yields a main-body profile consistent with the classic self-similar development of DM halos. In addition, we required the Jeans solutions to satisfy regular boundary conditions both at the center (finite pressure, round gravitational potential) and on the outskirts (finite overall mass). With these building blocks, we derived physical solutions, dubbed “<i>α<i/>-profiles”. We find the one with <i>α<i/> = 1.25, suitable for the Galaxy halo, to be intrinsically flatter at the center than the empirical NFW formula, yet steeper than the empirical Einasto profile. On scales of 10<sup>-1<sup/> deg it yields annihilation fluxes <i>lower<i/> by a factor <i>5<i/> than the former, yet <i>higher<i/> by a factor <i>10<i/> than the latter. Such fluxes will eventually fall within the reach of the <i>Fermi<i/> satellite. We show the effectiveness of the <i>α<i/>-profile in relieving the astrophysical uncertainties related to the macroscopic DM distribution, and discuss its expected performance as a tool instrumental in interpreting the upcoming <i>γ<i/>-ray data in terms of DM annihilation.