Concerning Colour: The Effect of Environment on Type Ia Supernova Colour in the Dark Energy Survey
Creators: name: Kelsey, L.
name: Sullivan, M.
name: Wiseman, P.
name: Armstrong, P.
name: Chen, R.
name: Brout, D.
name: Davis, T. M.
name: Dixon, M.
name: Frohmaier, C.
name: Galbany, L.
name: Graur, O.
name: Kessler, R.
name: Lidman, C.
name: Möller, A.
name: Popovic, B.
name: Rose, B.
name: Scolnic, D.
name: Smith, M.
name: Vincenzi, M.
name: Abbott, T. M. C.
name: Aguena, M.
name: Allam, S.
name: Alves, O.
name: Annis, J.
name: Bacon, D.
name: Bertin, E.
name: Bocquet, S.
name: Brooks, D.
name: Burke, D. L.
name: Rosell, A. Carnero
name: Kind, M. Carrasco
name: Carretero, J.
name: Costanzi, M.
name: da Costa, L. N.
name: Pereira, M. E. S.
name: Desai, S.
name: Diehl, H. T.
name: Everett, S.
name: Ferrero, I.
name: Frieman, J.
name: García-Bellido, J.
name: Gruen, D.
name: Gruendl, R. A.
name: Gschwend, J.
name: Gutierrez, G.
name: Hinton, S. R.
name: Hollowood, D. L.
name: Honscheid, K.
name: James, D. J.
name: Kuehn, K.
name: Kuropatkin, N.
name: Lewis, G. F.
name: Mena-Fernández, J.
name: Miquel, R.
name: Palmese, A.
name: Paz-Chinchón, F.
name: Pieres, A.
name: Malagón, A. A. Plazas
name: Raveri, M.
name: Rodriguez-Monroy, M.
name: Romer, A. K.
name: Sanchez, E.
name: Scarpine, V.
name: Schubnell, M.
name: Sevilla-Noarbe, I.
name: Suchyta, E.
name: Swanson, M. E. C.
name: Tarle, G.
name: Tucker, D. L.
name: Weaverdyck, N.
Publisher: name: arXiv
Year: 2022
Subjects: subject: Cosmology and Nongalactic Astrophysics (astro-ph.CO)
subject: Astrophysics of Galaxies (astro-ph.GA)
subject: FOS: Physical sciences
subject: FOS: Physical sciences

description: Recent analyses have found intriguing correlations between the colour ($c$) of type Ia supernovae (SNe Ia) and the size of their 'mass-step', the relationship between SN Ia host galaxy stellar mass ($M_\mathrm{stellar}$) and SN Ia Hubble residual, and suggest that the cause of this relationship is dust. Using 675 photometrically-classified SNe Ia from the Dark Energy Survey 5-year sample, we study the differences in Hubble residual for a variety of global host galaxy and local environmental properties for SN Ia subsamples split by their colour. We find a $3σ$ difference in the mass-step when comparing blue ($c&lt;0$) and red ($c&gt;0$) SNe. We observe the lowest r.m.s. scatter ($\sim0.14$ mag) in the Hubble residual for blue SNe in low mass/blue environments, suggesting that this is the most homogeneous sample for cosmological analyses. By fitting for $c$-dependent relationships between Hubble residuals and $M_\mathrm{stellar}$, approximating existing dust models, we remove the mass-step from the data and find tentative $\sim 2σ$ residual steps in rest-frame galaxy $U-R$ colour. This indicates that dust modelling based on $M_\mathrm{stellar}$ may not fully explain the remaining dispersion in SN Ia luminosity. Instead, accounting for a $c$-dependent relationship between Hubble residuals and global $U-R$, results in $\leq1σ$ residual steps in $M_\mathrm{stellar}$ and local $U-R$, suggesting that $U-R$ provides different information about the environment of SNe Ia compared to $M_\mathrm{stellar}$, and motivating the inclusion of galaxy $U-R$ colour in SN Ia distance bias correction.
description: 19 pages, 8 figures. Published in MNRAS