Environmental Dependence of Type Ia Supernova Luminosities from the YONSEI Supernova Catalog

Abstract: There is growing evidence for the dependence of Type Ia supernova (SN Ia) luminosities on their environments. While the impact of this trend on estimating cosmological parameters is widely acknowledged, the origin of this correlation is still under debate. In order to explore this problem, we first construct the YONSEI (YOnsei Nearby Supernova Evolution Investigation) SN catalog. The catalog consists of 1231 spectroscopically confirmed SNe Ia over a wide redshift range (0.01 < z < 1.37) from various SN surveys and includes the light-curve fit data from two independent light-curve fitters of SALT2 and MLCS2k2. For a sample of 674 host galaxies, we use the stellar mass and the star formation rate data in Kim et al. (2018). We find that SNe Ia in low-mass and star-forming host galaxies are $0.062\pm0.009$ mag and $0.057\pm0.010$ mag fainter than those in high-mass and passive hosts, after light-curve corrections with SALT2 and MLCS2k2, respectively. When only local environments of SNe Ia (e.g., locally star-forming and locally passive) are considered, this luminosity difference increases to $0.081\pm0.018$ mag for SALT2 and $0.072\pm0.018$ mag for MLCS2k2. Considering the significant difference in the mean stellar population age between the two environments, this result suggests that the origin of environmental dependence is most likely the luminosity evolution of SNe Ia with redshift.