The effect of environment on Type Ia supernovae in the Dark Energy Survey three-year cosmological sample
Analyses of Type Ia supernovae (SNe Ia) have found puzzling correlations between their standardized luminosities and host galaxy properties: SNe Ia in high-mass, passive hosts appear brighter than those in lower mass, star-forming hosts. We examine the host galaxies of SNe Ia in the Dark Energy Survey 3-yr spectroscopically confirmed cosmological sample, obtaining photometry in a series of ‘local’ apertures centred on the SN, and for the global host galaxy. We study the differences in these host galaxy properties, such as stellar mass and rest-frame U − R colours, and their correlations with SN Ia parameters including Hubble residuals. We find all Hubble residual steps to be >3σ in significance, both for splitting at the traditional environmental property sample median and for the step of maximum significance. For stellar mass, we find a maximal local step of 0.098 ± 0.018 mag; ∼0.03 mag greater than the largest global stellar mass step in our sample (0.070 ± 0.017 mag). When splitting at the sample median, differences between local and global U − R steps are small, both ∼0.08 mag, but are more significant than the global stellar mass step (0.057 ± 0.017 mag). We split the data into sub-samples based on SN Ia light-curve parameters: stretch (x1) and colour (c), finding that redder objects (c > 0) have larger Hubble residual steps, for both stellar mass and U − R, for both local and global measurements, of ∼0.14 mag. Additionally, the bluer (star-forming) local environments host a more homogeneous SN Ia sample, with local U − R rms scatter as low as 0.084 ± 0.017 mag for blue (c < 0) SNe Ia in locally blue U − R environments.
Kelsey, L; Sullivan, M; Smith, M; Wiseman, P; Brout, D; Davis, TM; Frohmaier, C; Galbany, L; Grayling, M; Gutiérrez, CP; Hinton, SR; Kessler, R; Lidman, C; Möller, A; Sako, M; Scolnic, D; Uddin, SA; Vincenzi, M; Abbott, TMC; Aguena, M; Allam, S; Annis, J; Avila, S; Bacon, D; Bertin, E; Brooks, D; Burke, DL; Carnero Rosell, A; Carrasco Kind, M; Carretero, J; Castander, FJ; Costanzi, M; da Costa, LN; Desai, S; Diehl, HT; Doel, P; Everett, S; Ferrero, I; Ferté, A; Flaugher, B; Fosalba, P; García-Bellido, J; Gerdes, DW; Gruen, D; Gruendl, RA; Gschwend, J; Gutierrez, G; Hollowood, DL; Honscheid, K; James, DJ; Kim, AG; Kuehn, K; Kuropatkin, N; Lahav, O; Lima, M; Marshall, JL; Martini, P; Menanteau, F; Miquel, R; Morgan, R; Ogando, RLC; Palmese, A; Paz-Chinchón, F; Plazas, AA; Romer, AK; Sánchez, C; Sanchez, E; Serrano, S; Sevilla-Noarbe, I; Suchyta, E; Tarle, G; Thomas, D; To, C; Varga, TN; Walker, AR; Wilkinson, RD
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