SALT3-NIR: Taking the Open-source Type Ia Supernova Model to Longer Wavelengths for Next-generation Cosmological Measurements
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 μm 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.
Pierel, JDR; Jones, DO; Kenworthy, WD; Dai, M; Kessler, R; Ashall, C; Do, A; Peterson, ER; Shappee, BJ; Siebert, MR; Barna, T; Brink, TG; Burke, J; Calamida, A; Camacho-Neves, Y; Jaeger, TD; Filippenko, AV; Foley, RJ; Galbany, L; Fox, OD; Gomez, S; Hiramatsu, D; Hounsell, R; Howell, DA; Jha, SW; Kwok, LA; Pérez-Fournon, I; Poidevin, F; Rest, A; Rubin, D; Scolnic, DM; Shirley, R; Strolger, LG; Tinyanont, S; Wang, Q
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