SALT3-NIR: Taking the Open-source Type Ia Supernova Model to Longer Wavelengths for Next-generation Cosmological Measurements
Justin Pierel, D. O. Jones, W. D. Kenworthy, Mi Dai, R. Keßler, C. Ashall, A. Do, Erik R. Peterson, B. J. Shappee, M. R. Siebert, Tyler Barna, Thomas G. Brink, J. Burke, A. Calamida, Yssavo Camacho-Neves, Thomas de Jaeger, A. V. Filippenko, R. J. Foley, L. Galbany, Ori D. Fox, Sebastián Gómez, D. Hiramatsu, Rebekah Hounsell, D. A. Howell, Saurabh W. Jha, Lindsey A. Kwok, I. Pérez‐Fournon, F. Poidevin, A. Rest, D. Rubin, D. Scolnic, R. Shirley, Louis-Gregory Strolger, Samaporn Tinyanont, Qinan Wang
Abstract
Abstract A large fraction of Type Ia supernova (SN Ia) observations over the next decade will be in the near-infrared (NIR), at wavelengths beyond the reach of the current standard light-curve model for SN Ia cosmology, SALT3 (∼2800–8700 Å central filter wavelength). To harness this new SN Ia sample and reduce future light-curve standardization systematic uncertainties, we train SALT3 at NIR wavelengths (SALT3-NIR) up to 2 μ m with the open-source model-training software SALTshaker , which can easily accommodate future observations. Using simulated data, we show that the training process constrains the NIR model to ∼2%–3% across the phase range (−20 to 50 days). We find that Hubble residual (HR) scatter is smaller using the NIR alone or optical+NIR compared to optical alone, by up to ∼30% depending on filter choice (95% confidence). There is significant correlation between NIR light-curve stretch measurements and luminosity, with stretch and color corrections often improving HR scatter by up to ∼20%. For SN Ia observations expected from the Roman Space Telescope, SALT3-NIR increases the amount of usable data in the SALT framework by ∼20% at redshift z ≲ 0.4 and by ∼50% at z ≲ 0.15. The SALT3-NIR model is part of the open-source SNCosmo and SNANA SN Ia cosmology packages.