Photometric properties of intermediate redshift Type Ia Supernovae observed by SDSS-II Supernova Survey

TL;DR

This study analyzes multi-band light curves of 328 intermediate redshift Type Ia supernovae from SDSS-II, revealing differences in host galaxy properties, extinction laws, and suggesting two intrinsic SN Ia types with distinct dust obscuration characteristics.

Contribution

It introduces the Multi-band Stretch Method for light curve analysis and uncovers variations in host galaxy dust extinction properties among SNe Ia.

Findings

Red host galaxies host SNe Ia with narrower light curves.

Blue host galaxies show diverse light curve widths.

Extinction law parameter Rv varies with host galaxy type.

Abstract

We have analyzed multi-band light curves of 328 intermediate redshift (0.05 <= z < 0.24) type Ia supernovae (SNe Ia) observed by the Sloan Digital Sky Survey-II Supernova Survey (SDSS-II SN Survey). The multi-band light curves were parameterized by using the Multi-band Stretch Method, which can simply parameterize light curve shapes and peak brightness without dust extinction models. We found that most of the SNe Ia which appeared in red host galaxies (u - r > 2.5) don't have a broad light curve width and the SNe Ia which appeared in blue host galaxies (u - r < 2.0) have a variety of light curve widths. The Kolmogorov-Smirnov test shows that the colour distribution of SNe Ia appeared in red / blue host galaxies is different (significance level of 99.9%). We also investigate the extinction law of host galaxy dust. As a result, we find the value of Rv derived from SNe Ia with medium light curve width is consistent with the standard Galactic value. On the other hand, the value of Rv derived from SNe Ia that appeared in red host galaxies becomes significantly smaller. These results indicate that there may be two types of SNe Ia with different intrinsic colours, and they are obscured by host galaxy dust with two different properties.