On the origin of Sérsic profiles of galaxies and Einasto profiles of dark-matter halos
arXiv:1605.00680 · doi:10.1017/S1743921316009455
Abstract
The surface-brightness profiles of galaxies I(R) and the density profiles of dark-matter halos rho(r) are well represented by the same analytic function, named after either Sérsic, I~exp[-(R/R*)^(1/m)], or Einasto, rho~[exp[-(r/r*)^alpha], where R* and r* are characteristic radii. Systems with high Sérsic index m (or low Einasto index alpha) have steep central profiles and shallow outer profiles, while systems with low m (or high alpha) have shallow central profiles and steep profiles in the outskirts. We present the results of idealized numerical experiments which suggest that the origin of these profiles can be traced back to the initial density fluctuation field: high-alpha (low-m) systems form in smooth regions via few mergers, while low-alpha (high-m) systems form in clumpy regions via several mergers.
3 pages, 2 figures, Proceedings of IAU Symposium 321, "Formation and evolution of galaxy outskirts", Eds. A. Gil de Paz, J. C. Lee & J. H. Knapen, Cambridge University Press, Cambridge