ZTF SN Ia DR2: Colour standardisation of type Ia supernovae and its dependence on the environment
Year: 2025
Type: article
Abstract: Context. As type Ia supernova cosmology transitions from a statistics-dominated to a systematics-dominated era, it is crucial to understand the remaining unexplained uncertainties that affect their luminosity, such as those stemming from astrophysical biases. Type Ia supernovae are standardisable candles whose absolute magnitude reaches a scatter of typically 0.15 mag when empirical correlations with their light-curve stretch and colour and with their environmental properties are accounted for. Aims. We investigate the dependence of the standardisation process of type Ia supernovae on the astrophysical environment to ultimately reduce their scatter in magnitude. We focus on colour standardisation. Methods. We used the volume-limited ZTF SN Ia DR2 sample, which offers unprecedented statistics for the low-redshift (z < 0.06) range. We first studied the colour distribution with a focus on the effects of dust to then select a dustless subsample of objects that originated in environments with a low stellar mass and in the outskirts of their host galaxies. We then examined the colour-residual relation and its associated parameter β. Finally, we investigated the colour dependence of the environment-dependent magnitude offsets (steps) to separate their intrinsic and extrinsic components. Results. Our sample of nearly 1000 supernovae probes the red tail of the colour distribution up to c = 0.8. The dustless sample exhibits a significantly shorter red tail (4.3σ) than the whole sample, but the distributions around c ∼ 0 are similar for both samples. This suggests that the reddening above c ≥ 0.2 is dominated by interstellar dust absorption of the host and that the remaining colour scatter has an intrinsic origin. The colour-residual relation is linear with light-curve colour. We found indications of a potential evolution of β with the stellar host mass, with β ∼ 3.6 for low-mass galaxies, compared to β = 3.05 ± 0.06 for the full sample. Finally, in contrast to recent claims from the literature, we found no evolution of steps as a function of light-curve colour. This suggests that dust may not be the dominating mechanism for the dependence on the environment of the magnitude of type Ia supernovae.
Authors: M. Ginolin, M. Rigault, Y. Copin, B. Popovic, G. Dimitriadis, A. Goobar, J. Johansson, K. Maguire, J. Nordin, M. Smith, M. Aubert, C. Barjou-Delayre, U. Burgaz, B. Carreres, S. Dhawan, M. Deckers, F. Feinstein, D. Fouchez, L. Galbany, C. Ganot, T. de Jaeger, Y.-L. Kim, D. Kuhn, L. Lacroix, T. E. Müller-Bravo, P. Nugent, B. Racine, P. Rosnet, D. Rosselli, F. Ruppin, J. Sollerman, J. H. Terwel, A. Townsend, R. Dekany, M. Graham, M. Kasliwal, S. L. Groom, J. Purdum, B. Rusholme, S. van der Walt
Institutions: Lyon 1 Université, Centre National de la Recherche Scientifique, Institut National de Physique Nucléaire et de Physique des Particules, Institut de Physique des 2 Infinis de Lyon, Trinity College Dublin, Stockholm University, Humboldt-Universität zu Berlin, Lancaster University, Université Clermont Auvergne, Laboratoire de Physique de Clermont Auvergne, Duke University, Aix-Marseille Université, Centre de physique des particules de Marseille, Institute of Astronomy, Institute of Space Sciences, Institut d'Estudis Espacials de Catalunya, Sorbonne Université, Laboratoire de Physique Nucléaire et de Hautes Énergies, Lawrence Berkeley National Laboratory, University of California, Berkeley, Nordic Optical Telescope, California Institute of Technology, Infrared Processing and Analysis Center, University of Cambridge
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: green
Funders: National Science Foundation, California Institute of Technology, Northwestern University, University of Washington, University of Warwick, European Commission, Trinity College Dublin, Agence Nationale de la Recherche, Weizmann Institute of Science, Knut och Alice Wallenbergs Stiftelse, Vetenskapsrådet, Ministerio de Ciencia e Innovación, Stockholms Universitet, Horizon 2020 Framework Programme, Science and Technology Facilities Council, Deutsches Elektronen-Synchrotron, Agència de Gestió d'Ajuts Universitaris i de Recerca, Agencia Estatal de Investigación, Institut National de Physique Nucléaire et de Physique des Particules, H2020 European Research Council
Awards: G1175115578, Charting new physics with time-domain astronomy, G1530525900, G1855990336, The SED Machine: an Efficient Transient Classifier, G1938211519, G2018370741, G2262748287, G2309174360, G2601397997, Exploring & Exploiting the Dynamic Optical Sky, G2849891921, G288263039, G300979063, G3243338908, G3439265645, G3480869486, ZWICKY TRANSIENT FACILITY, G3518538256, G3681454997, G4019291869, G4042783231, G425668148, Mapping the cosmic expansion history with Type Ia supernovae, G430777504, G4655338613, Type Ia supernovae: from explosions to cosmology, G4881091899, G5077476177, G5080475149, G5195188938, G5421974903, Understanding Type Ia SuperNovae for Accurate Cosmology, G5805502524, Lancaster University Observational Astrophysics 2021-2024, G5852091828, G617610489, G6197919437, PIRE: GROWTH: Global Relay of Observatories Watching Transients Happen, G6308328899, G6359813416, G6853635150, G7001747737, G7099350353, G7137047011, G7169023097, G7297159037, G7441047379, G7476612352, G8324017279, G8775481269, A golden nearby SN sample from the Zwicky Transient Facility-II Survey (ZTF-II), G8924351487, G917015191, G99296377
OpenAlex ID: W7111260068
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