The Influence of Central Density on the Brightness of Type Ia Supernovae

We present details of a statistical study investigating the role of the central density of the progenitor white dwarf on the brightness of a Type Ia supernova. We present results from a suite of two-dimensional simulations varying the central density at flame ignition. We find that the production of Fe-group material does not significantly change with increased progenitor central density, but that the mass of stable Fe-group isotopes is tightly correlated with central density. The result is a decrease in the production of ⁵⁶Ni, which we attribute to a higher rate of neutronization occurring at higher density. We present details of our models including the distribution of ⁵⁶Ni and quantify trends of ⁵⁶Ni production. We also relate the variations in central density to the age of the host galaxy stellar population through the main-sequence lifetime and the white dwarf cooling time, which is the elapsed time between the formation of the white dwarf and the onset of accretion. This density-age relationship, along with our results, allows us to obtain the observed relationship between the age of the host galaxy and the average brightness of an event.

This work was supported by NASA under grant No. NNX09AD19G and utilized resources at the New York Center for Computational Sciences at Stony Brook University/Brookhaven National Laboratory, which is supported by the U.S. Department of Energy under Contract No. DE-AC02-98CH10886 and by the State of New York.