Anisotropies in the Neutrino Fluxes and Heating Profiles in Two‐dimensional, Time‐dependent, Multigroup Radiation Hydrodynamics Simulations of Rotating Core‐Collapse Supernovae

Using the 2D multi-group, flux-limited diffusion version of the codeVULCAN/2D, that also incorporates rotation, we have calculated the collapse,bounce, shock formation, and early post-bounce evolutionary phases of acore-collapse supernova for a variety of initial rotation rates. This is thefirst series of such multi-group calculations undertaken in supernova theorywith fully multi-D tools. We find that though rotation generatespole-to-equator angular anisotropies in the neutrino radiation fields, themagnitude of the asymmetries is not as large as previously estimated. Moreover,we find that the radiation field is always more spherically symmetric than thematter distribution, with its plumes and convective eddies. We present thedependence of the angular anisotropy of the neutrino fields on neutrinospecies, neutrino energy, and initial rotation rate. Only for our most rapidlyrotating model do we start to see qualitatively different hydrodynamics, butfor the lower rates consistent with the pre-collapse rotational profilesderived in the literature the anisotropies, though interesting, are modest.This does not mean that rotation does not play a key role in supernovadynamics. The decrease in the effective gravity due to the centripetal effectcan be quite important. Rather, it means that when a realistic mapping betweeninitial and final rotational profiles and 2D multi-groupradiation-hydrodynamics are incorporated into collapse simulations theanisotropy of the radiation fields may be only a secondary, not a pivotalfactor, in the supernova mechanism.Comment: Includes 11 low-resolution color figures, accepted to the Astrophysical Journal (June 10, 2005; V. 626); high-resolution figures and movies available from the authors upon reques