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

**Authors:** Young-Lo Kim, Yijung Kang, Young-Wook Lee  
**arXiv:** [1908.10375](https://arxiv.org/abs/1908.10375)  
**Date:** 2019-08-27  
**Summary page:** https://www.summarizepaper.com/en/arxiv-id/1908.10375v1/

## Key points

- Type Ia supernova (SN Ia) luminosities dependence on their environments is a growing area of research
- Dependence has significant implications for estimating cosmological parameters
- YONSEI SN catalog was constructed, including 1231 spectroscopically confirmed SNe Ia over a wide redshift range (0.01 < z < 1.37)
- Catalog uses stellar mass and star formation rate data to investigate the relationship between SN Ia luminosity and environment for a sample of 674 host galaxies
- 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 are considered, this luminosity difference increases to $0.081\pm0.018$ mag for SALT2 and $0.072\pm0.018$ mag for MLCS2k2.
- The significant difference in mean stellar population age between the two environments suggests that the origin of environmental dependence is most likely due to the luminosity evolution of SNe Ia with redshift rather than any intrinsic property related to host galaxy properties such as metallicity or dust extinction.

## Summary

The dependence of Type Ia supernova (SN Ia) luminosities on their environments is a growing area of research, as it has significant implications for estimating cosmological parameters. The origin of this correlation, however, remains under debate. To address this problem, the YONSEI (YOnsei Nearby Supernova Evolution Investigation) SN catalog was constructed, which includes 1231 spectroscopically confirmed SNe Ia over a wide redshift range (0.01 < z < 1.37) from various SN surveys and light-curve fit data from two independent light-curve fitters of SALT2 and MLCS2k2. For a sample of 674 host galaxies, the catalog uses stellar mass and star formation rate data to investigate the relationship between SN Ia luminosity and environment. The results show 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. The significant difference in mean stellar population age between the two environments suggests that the origin of environmental dependence is most likely due to the luminosity evolution of SNe Ia with redshift rather than any intrinsic property related to host galaxy properties such as metallicity or dust extinction.