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Published March 2025 | Version Published
Journal Article Open

ZTF SN Ia DR2: Environmental dependencies of stretch and luminosity for a volume-limited sample of 1000 type Ia supernovae

Creators

  • 1. ROR icon Claude Bernard University Lyon 1
  • 2. ROR icon Lancaster University
  • 3. ROR icon Trinity College Dublin
  • 4. ROR icon Stockholm University
  • 5. ROR icon Humboldt-Universität zu Berlin
  • 6. ROR icon National Research Council Canada
  • 7. ROR icon University of Clermont Auvergne
  • 8. ROR icon Laboratoire de Physique Nucléaire et de Hautes Énergies
  • 9. ROR icon Center for Particle Physics of Marseilles
  • 10. ROR icon Duke University
  • 11. ROR icon University of Cambridge
  • 12. ROR icon Institute of Space Sciences
  • 13. ROR icon Institut d'Estudis Espacials de Catalunya
  • 14. ROR icon Deutsches Elektronen-Synchrotron DESY
  • 15. ROR icon Lawrence Berkeley National Laboratory
  • 16. ROR icon University of California, Berkeley
  • 17. ROR icon California Institute of Technology
  • 18. ROR icon University of Washington
  • 19. ROR icon Infrared Processing and Analysis Center

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.

Copyright and License

© The Authors 2025.

Open Access article, published by EDP Sciences, under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Acknowledgement

Based on observations obtained with the Samuel Oschin Telescope 48-inch and the 60-inch Telescope at the Palomar Observatory as part of the Zwicky Transient Facility project. ZTF is supported by the National Science Foundation under Grants No. AST-1440341 and AST-2034437 and a collaboration including current partners Caltech, IPAC, the Weizmann Institute of Science, the Oskar Klein Center at Stockholm University, the University of Maryland, Deutsches Elektronen-Synchrotron and Humboldt University, the TANGO Consortium of Taiwan, the University of Wisconsin at Milwaukee, Trinity College Dublin, Lawrence Livermore National Laboratories, IN2P3, University of Warwick, Ruhr University Bochum, Northwestern University and former partners the University of Washington, Los Alamos National Laboratories, and Lawrence Berkeley National Laboratories. Operations are conducted by COO, IPAC, and UW. SED Machine is based upon work supported by the National Science Foundation under Grant No. 1106171 The ZTF forced-photometry service was funded under the Heising-Simons Foundation grant #12540303 (PI: Graham). This project has received funding from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation program (grant agreement n 759194 - USNAC). MMK acknowledges generous support from the David and Lucille Packard Foundation. UB, MD, GD, KM and JHT are supported by the H2020 European Research Council grant no. 758638. LG acknowledges financial support from the Spanish Ministerio de Ciencia e Innovación (MCIN) and the Agencia Estatal de Investigación (AEI) 10.13039/501100011033 under the PID2020-115253GA-I00 HOSTFLOWS project, from Centro Superior de Investigaciones Científicas (CSIC) under the PIE project 20215AT016 and the program Unidad de Excelencia María de Maeztu CEX2020-001058-M, and from the Departament de Recerca i Universitats de la Generalitat de Catalunya through the 2021-SGR-01270 grant. This work has been supported by the research project grant “Understanding the Dynamic Universe” funded by the Knut and Alice Wallenberg Foundation under Dnr KAW 2018.0067, Vetenskapsrådet, the Swedish Research Council, project 2020-03444 and the G.R.E.A.T research environment, project number 2016-06012. YLK has received funding from the Science and Technology Facilities Council [grant number ST/V000713/1]. This work has been supported by the Agence Nationale de la Recherche of the French government through the program ANR-21-CE31-0016-03. TEMB acknowledges financial support from the Spanish Ministerio de Ciencia e Innovación (MCIN), the Agencia Estatal de Investigación (AEI) 10.13039/501100011033, and the European Union Next Generation EU/PRTR funds under the 2021 Juan de la Cierva program FJC2021-047124-I and the PID2020-115253GA-I00 HOSTFLOWS project, from Centro Superior de Investigaciones Científicas (CSIC) under the PIE project 20215AT016, and the program Unidad de Excelencia María de Maeztu CEX2020-001058-M. LH is funded by the Irish Research Council under grant number GOIPG/2020/1387. SD acknowledges support from the Marie Curie Individual Fellowship under grant ID 890695 and a Junior Research Fellowship at Lucy Cavendish College.

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Additional details

Related works

Is new version of
Discussion Paper: arXiv:2405.20965 (arXiv)

Funding

National Science Foundation
AST-1440341
National Science Foundation
AST-2034437
National Science Foundation
AST-1106171
Heising-Simons Foundation
12540303
European Research Council
759194
David and Lucile Packard Foundation
European Research Council
758638
Ministerio de Ciencia, Innovación y Universidades
Agencia Estatal de Investigación
HOSTFLOWS PID2020-115253GA-I00
Consejo Superior de Investigaciones Científicas
20215AT016
Ministerio de Ciencia, Innovación y Universidades
Unidad de Excelencia María de Maeztu CEX2020-001058-M
Departament de Recerca i Universitats
2021-SGR-01270
Knut and Alice Wallenberg Foundation
2018.0067
Swedish Research Council
2020-03444
Swedish Research Council
2016-06012
Science and Technology Facilities Council
ST/V000713/1
Agence Nationale de la Recherche
ANR-21-CE31-0016-03
European Union
2021 Juan de la Cierva Program FJC2021-047124-I
Irish Research Council
GOIPG/2020/1387
Marie Curie
890695
University of Cambridge
Lucy Cavendish College -

Dates

Accepted
2025-01-31
Available
2025-03-14
Published online

Caltech Custom Metadata

Caltech groups
Astronomy Department, Infrared Processing and Analysis Center (IPAC), Zwicky Transient Facility, Division of Physics, Mathematics and Astronomy (PMA)
Publication Status
Published