SALT2 Versus SALT3: Updated Model Surfaces and Their Impacts on Type Ia Supernova Cosmology

Abstract

For the past decade, SALT2 has been the most common model used to fit Type Ia supernova (SN Ia) light curves for dark energy analyses. Recently, the SALT3 model was released, which upgraded a number of model features but has not yet been used for measurements of dark energy. Here, we evaluate the impact of switching from SALT2 to SALT3 for a SN cosmology analysis. We train SALT2 and SALT3 on an identical training sample of 1083 well-calibrated Type Ia supernovae, ensuring that any differences found come from the underlying model framework. We publicly release the results of this training (the SALT "surfaces"). We then run a cosmology analysis on the public Dark Energy Survey 3-Year Supernova data sample (DES-SN3YR), and on realistic simulations of those data. We provide the first estimate of the SN+CMB systematic uncertainty arising from the choice of SALT model framework (i.e. SALT2 versus SALT3), $\Delta w=+0.001\pm 0.005$ -- a negligible effect at the current level of dark energy analyses. We also find that the updated surfaces are less sensitive to photometric calibration uncertainties than previous SALT2 surfaces, with the average spectral energy density dispersion reduced by a factor of two over optical wavelengths. This offers an opportunity to reduce the contribution of calibration errors to SN cosmology uncertainty budgets.

19 pages, 13 figures, accepted by MNRAS

References in corpus (10)

• Five-Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Cosmological Interpretation
• Supernova Constraints and Systematic Uncertainties from the First 3 Years of the Supernova Legacy Survey
• CfA3: 185 Type Ia Supernova Light Curves from the CfA
• Correcting Type Ia Supernova Distances for Selection Biases and Contamination in Photometrically Identified Samples
• The Carnegie Supernova Project I: Third Photometry Data Release of Low-Redshift Type Ia Supernovae and Other White Dwarf Explosions
• Type Ia Supernovae as Stellar Endpoints and Cosmological Tools
• Dos and don'ts of reduced chi-squared
• A Revised SALT2 Surface for Fitting Type Ia Supernova Light Curves
• A Reference Survey for Supernova Cosmology with the Nancy Grace Roman Space Telescope
• Initial Evaluation of SNEMO2 and SNEMO7 Standardization Derived From Current Light Curves of Type Ia Supernovae

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• ZTF SN Ia DR2: Improved SN Ia colors through expanded dimensionality with SALT3+
• Dark Energy Survey: DESI-Independent Angular BAO Measurement
• ZTF SN Ia DR2 follow-up: Exploring the origin of the Type Ia supernova host galaxy step through Si II velocities
• Characterising the Standardisation Properties of Type Ia Supernovae in the z band with Hierarchical Bayesian Modelling
• Training Custom Light Curve Models of SN Ia Sub-Populations Selected According to Host Galaxy Properties
• Joint Curvature and Growth Rate measurements with Supernova Peculiar Velocities and the CMB
• Searching for Type Ia Supernovae in the Dark Energy Spectroscopic Instrument