Luminosity distributions of Type Ia Supernovae

Chris Ashall; Paolo Mazzali; Michele Sasdelli; Simon Prentice

doi:10.1093/mnras/stw1214

paper

Luminosity distributions of Type Ia Supernovae

arXiv:1605.05507 · doi:10.1093/mnras/stw1214

Abstract

We have assembled a dataset of 165 low redshift, $z <$ 0.06, publicly available type Ia supernovae (SNe Ia). We produce maximum light magnitude ( $M_{B}$ and $M_{V}$ ) distributions of SNe Ia to explore the diversity of parameter space that they can fill. Before correction for host galaxy extinction we find that the mean $M_{B}$ and $M_{V}$ of SNe Ia are $- 18.58 \pm 0.07$ mag and $- 18.72 \pm 0.05$ mag respectively. Host galaxy extinction is corrected using a new method based on the SN spectrum. After correction, the mean values of $M_{B}$ and $M_{V}$ of SNe Ia are $- 19.10 \pm 0.06$ and $- 19.10 \pm 0.05$ mag respectively. After correction for host galaxy extinction, `normal' SNeIa ( $Δ m_{15} (B) < 1.6$ mag) fill a larger parameter space in the Width-Luminosity Relation (WLR) than previously suggested, and there is evidence for luminous SNe Ia with large $Δ m_{15} (B)$ . We find a bimodal distribution in $Δ m_{15} (B)$ , with a pronounced lack of transitional events at $Δ m_{15} (B)$ =1.6 mag. We confirm that faster, low-luminosity SNe tend to come from passive galaxies. Dividing the sample by host galaxy type, SNe Ia from star-forming (S-F) galaxies have a mean $M_{B} = - 19.20 \pm 0.05$ mag, while SNe Ia from passive galaxies have a mean $M_{B} = - 18.57 \pm 0.24$ mag. Even excluding fast declining SNe, `normal' ( $M_{B} < - 18$ mag) SNe Ia from S-F and passive galaxies are distinct. In the $V$ -band, there is a difference of 0.4 $\pm$ 0.13 mag between the median ( $M_{V}$ ) values of the `normal' SN Ia population from passive and S-F galaxies. This is consistent with ( $\sim 15 \pm$ 10)% of `normal' SNe Ia from S-F galaxies coming from an old stellar population.

Accepted for publication in MNRAS

Luminosity distributions of Type Ia Supernovae

Abstract

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