ZTF SNe Ia DR2: Towards cosmology-grade ZTF supernova light curves using scene modeling photometry

The Zwicky Transient Facility (ZTF) is conducting a wide-field survey of the northern sky in three optical bands and the collaboration cosmology working group has released 3628 spectroscopically confirmed Type Ia supernovae (SNe Ia) discovered during its first 2.5 years of operation. This "ZTF SN Ia DR2" sample is the largest SN Ia dataset to date. Fully exploiting this dataset to improve understanding of the properties of dark energy requires a photometric accuracy of O(0.1%). This can be achieved using Scene Modeling Photometry (SMP), which is optimal to extract a transient signal (SN) from a complex background (its host), while ensuring a common flux estimator with nearby stars used as calibration reference. In this paper, we present the status of the SMP development and use it to assess the precision and accuracy of the ZTF SN Ia DR2 force photometry light curves. We reach a repeatability of the star observations better than 1%. However, we have identified a new sensor effect, dubbed "pocket-effect", which distorts the Point Spread Function (PSF) in a flux-dependent manner leading to non-linearities in the photometry of a few percent. Correcting for this effect requires time- and sensor-dependent corrections to be applied at the pixel level, which is currently under development. This effects affects all light curve releases to date -- both from forced photometry and scene modelling preventing ZTF SN Ia DR2 to be used for accurate cosmological inference. Comparing the SMP and forced photometry measurements, we find that stretch and color estimated from both processings are consistent, aside from a 10 mmag shift in color. This assess the robustness of results presented as part of the the ZTF SN Ia DR2 release. The absolute calibration however shifts by 90 mmag. A reprocessing of the full ZTF SN Ia DR2 dataset using the SMP method is currently in progress.

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ArXiv.org
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2025-09-04
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Gamma-ray bursts and supernovae
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article

ZTF SNe Ia DR2: Towards cosmology-grade ZTF supernova light curves using scene modeling photometry

Avery Wold, T.E Müller-Bravo, Ludovic Lacroix, K. Maguire et al.
ArXiv.org
Gamma-ray bursts and supernovae
article

ZTF SNe Ia DR2: Towards cosmology-grade ZTF supernova light curves using scene modeling photometry

Avery Wold, T.E Müller-Bravo, Ludovic Lacroix, K. Maguire, J. Terwel, G. Dimitriadis, M. C. Smith, L. Galbany, Alan R. Townsend, M Ginolin, Jean-Marc Colley, J. Nordin, M. Betoule, M Aubert, A. Goobar, M. Le Jeune, F. Feinstein, M. J. Graham, Medhat Osman, Mark E. Bernard, M. Rigault, D. Fouchez, J Sollerman, Thomas de Jaeger, S. Bongard, Eric C. Bellm, J. Neveu, Bastien Carreres, J. Johansson, Deanna Kuhn, R.R Laher, B Popovic, U. Burgaz, Roger M. Smith, B. Racine, N. Regnault, P. Rosnet, D. Rosselli, C Barjou
article en

Abstract

The Zwicky Transient Facility (ZTF) is conducting a wide-field survey of the northern sky in three optical bands and the collaboration cosmology working group has released 3628 spectroscopically confirmed Type Ia supernovae (SNe Ia) discovered during its first 2.5 years of operation. This "ZTF SN Ia DR2" sample is the largest SN Ia dataset to date. Fully exploiting this dataset to improve understanding of the properties of dark energy requires a photometric accuracy of O(0.1%). This can be achieved using Scene Modeling Photometry (SMP), which is optimal to extract a transient signal (SN) from a complex background (its host), while ensuring a common flux estimator with nearby stars used as calibration reference. In this paper, we present the status of the SMP development and use it to assess the precision and accuracy of the ZTF SN Ia DR2 force photometry light curves. We reach a repeatability of the star observations better than 1%. However, we have identified a new sensor effect, dubbed "pocket-effect", which distorts the Point Spread Function (PSF) in a flux-dependent manner leading to non-linearities in the photometry of a few percent. Correcting for this effect requires time- and sensor-dependent corrections to be applied at the pixel level, which is currently under development. This effects affects all light curve releases to date -- both from forced photometry and scene modelling preventing ZTF SN Ia DR2 to be used for accurate cosmological inference. Comparing the SMP and forced photometry measurements, we find that stretch and color estimated from both processings are consistent, aside from a 10 mmag shift in color. This assess the robustness of results presented as part of the the ZTF SN Ia DR2 release. The absolute calibration however shifts by 90 mmag. A reprocessing of the full ZTF SN Ia DR2 dataset using the SMP method is currently in progress.

ArXiv.org
Université Paris Cité (FR), Laboratoire AstroParticule et Cosmologie (FR), Centre de physique des particules de Marseille (FR), Laboratoire de Physique Nucléaire et de Hautes Énergies (FR), Laboratoire de Physique des 2 Infinis Irène Joliot-Curie (FR), Institute of Nuclear Physics of Lyon (FR), Institut de Physique des 2 Infinis de Lyon (FR)
Openalex Percentile: Top 81%
Gamma-ray bursts and supernovae
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