Reconciling Volumetric and Individual Galaxy Type Ia Supernova Rates

TL;DR

This paper introduces a new model for type Ia supernova rates based on a simple delay time distribution, reconciling local galaxy observations with high-redshift volumetric rates, and demonstrating improved fit over existing models.

Contribution

The authors propose a novel delay time distribution-based model for supernova rates that aligns well with observational data and improves upon the traditional A+B model.

Findings

The new model predicts a prompt fraction of 0.11, consistent with high-redshift volumetric rate studies.

It fits observational data significantly better than the A+B model.

The model is validated against star formation rates from the Illustris-1 simulation.

Abstract

Significant observational effort has been devoted to determining volumetric type Ia supernova rates at high redshifts, leading to clues about the nature of Ia supernova progenitors and constraints on the iron production in the universe. A complementary approach is to investigate type Ia supernova rates in individual, more nearby, galaxies. The popular A+B model for the specific supernova rate, while reliable for a wide range of galaxy properties, diverges for large specific star formation rates. Applying it outside its range of validity could lead to the prediction of excessive type Ia supernova rates. Moreover, the A+B model it is not directly derived from a delay time distribution. We here introduce a new model which is explicitly motivated by a simple delay time distribution composed of a prompt and a delayed component. The model is in remarkably good agreement with current observational constraints. It yields a prompt fraction of $f_{p}= 0.11^{+0.10}_{-0.06}$ in agreement with results based on volumetric rates of type Ia supernovae at high redshift (Rodney et al. 2014). The model is tested against realistic star formation rates from the Illustris-1 simulation and is found to be self consistent in the asymptotic limits. An analytic function that encapsulates the features of the new model is shown to be in excellent agreement with the data. In terms of goodness of fit, the new model is strongly preferred over the A+B model. At $\log{({\rm sSFR})} \gtrsim -9$ there are no constraints from observations. Observations in this regime will further constrain the delay time distribution of type Ia supernovae at short delay times.