ZTF SN Ia DR2: Environmental dependencies of stretch and luminosity for a volume-limited sample of 1000 type Ia supernovae
Year: 2025
Type: article
Abstract: Context. Type Ia supernova (SN Ia) cosmology studies will soon be dominated by systematic, uncertainties, rather than statistical ones. Thus, it is crucial to understand the unknown phenomena potentially affecting their luminosity that may remain, such as astrophysical biases. For their accurate application in such studies, SN Ia magnitudes need to be standardised; namely, they must be corrected for their correlation with the light-curve width and colour. Aims. Here, we investigate how the standardisation procedure used to reduce the scatter of SN Ia luminosities is affected by their environment. Our aim is to reduce scatter and improve the standardisation process. Methods. We first studied the SN Ia stretch distribution, as well as its dependence on environment, as characterised by local and global (g − z) colour and stellar mass. We then looked at the standardisation parameter, α, which accounts for the correlation between residuals and stretch, along with its environment dependency and linearity. Finally, we computed the magnitude offsets between SNe in different astrophysical environments after the colour and stretch standardisations (i.e. steps). This analysis has been made possible thanks to the unprecedented statistics of the volume-limited Zwicky Transient Facility (ZTF) SN Ia DR2 sample. Results. The stretch distribution exhibits a bimodal behaviour, as previously found in the literature. However, we find the distribution to be dependent on environment. Specifically, the mean stretch modes decrease with host stellar mass, at a 9.2σ significance. We demonstrate, at the 13.4σ level, that the stretch-magnitude relation is non-linear, challenging the usual linear stretch-residuals relation currently used in cosmological analyses. In fitting for a broken-α model, we did indeed find two different slopes between stretch regimes (x1 ≶ x10 with x10 = −0.48 ± 0.08): αlow = 0.271 ± 0.011 and αhigh = 0.083 ± 0.009, comprising a difference of Δα = −0.188 ± 0.014. As the relative proportion of SNe Ia in the high-stretch and low-stretch modes evolves with redshift and environment, this implies that a single-fitted α also evolves with the redshift and environment. Concerning the environmental magnitude offset γ, we find it to be greater than 0.12 mag, regardless of the considered environmental tracer used (local or global colour and stellar mass), all measured at the ≥5σ level. When accounting for the non-linearity of the stretch, these steps increase to ∼0.17 mag, measured with a precision of 0.01 mag. Such strong results highlight the importance of using a large volume-limited dataset to probe the underlying SN Ia-host correlations.
Authors: M. Ginolin, M. Rigault, M. Smith, Y. Copin, F. Ruppin, G. Dimitriadis, A. Goobar, J. Johansson, K. Maguire, J. Nordin, M. Amenouche, M. Aubert, C. Barjou-Delayre, M. Betoule, U. Burgaz, B. Carreres, M. Deckers, S. Dhawan, F. Feinstein, D. Fouchez, L. Galbany, C. Ganot, L. Harvey, T. de Jaeger, W. D. Kenworthy, Y.-L. Kim, M. Kowalski, D. Kuhn, L. Lacroix, T. E. Müller-Bravo, P. Nugent, B. Popovic, B. Racine, P. Rosnet, D. Rosselli, J. Sollerman, J. H. Terwel, A. Townsend, J. Brugger, E. C. Bellm, M. M. Kasliwal, S. Kulkarni, R. R. Laher, F. J. Masci, R. L. Riddle, Y. Sharma
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, Herzberg Institute of Astrophysics, National Research Council Canada, Université Clermont Auvergne, Laboratoire de Physique de Clermont Auvergne, Sorbonne Université, Laboratoire de Physique Nucléaire et de Hautes Énergies, 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, Lancaster University, Deutsches Elektronen-Synchrotron DESY, Lawrence Berkeley National Laboratory, University of California, Berkeley, Nordic Optical Telescope, California Institute of Technology, University of Washington, Infrared Processing and Analysis Center
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, Irish Research Council, Generalitat de Catalunya, 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, Agencia Estatal de Investigación, Institut National de Physique Nucléaire et de Physique des Particules, H2020 European Research Council
Awards: Charting new physics with time-domain astronomy, G1855990336, The SED Machine: an Efficient Transient Classifier, G2018370741, G2064873908, G2262748287, G2309174360, G2601397997, Exploring & Exploiting the Dynamic Optical Sky, G2849891921, G3005324705, G300979063, G3243338908, G3439265645, G3480869486, ZWICKY TRANSIENT FACILITY, G3518538256, G3681454997, G4042783231, G425668148, Mapping the cosmic expansion history with Type Ia supernovae, G430777504, G4655338613, Type Ia supernovae: from explosions to cosmology, G4881091899, G5077476177, G5080475149, G5421974903, Understanding Type Ia SuperNovae for Accurate Cosmology, G5805502524, Lancaster University Observational Astrophysics 2021-2024, G617610489, G6197919437, G6308328899, G6359813416, G6513613686, G6853635150, G7099350353, G7137047011, G7169023097, G7297159037, G7441047379, G7476612352, G7510076775, GREAT: Gravitational Radiation and Electromagnetic Astrophysical Transients, G8324017279, G8511709958, G8775481269, A golden nearby SN sample from the Zwicky Transient Facility-II Survey (ZTF-II), G8924351487, G917015191
OpenAlex ID: W7110888546
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