Properties of Near-Infrared Type Ia Supernovae Light Curves

As a result of the standardizability of SNe Ia light curves over a wide range of photometric bands, they are used as standard candles to accurately measure distances in the cosmos up to z ≈ 1 [22]. As dust extinction is smaller in the NIR than in the optical [21] there is less dispersion seen in the peak brightnesses of SNe Ia, making them truly standard candles. We use SNPY to fit light curves for 192 SNe Ia. The mean of all Hubble residuals of our sample is ≈ 0.101 mag with a standard deviation of ≈ 0.234 mag. After applying an original set of cuts, the mean of 173 Hubble residuals reduces to ≈ 0.080 mag with a standard deviation of 0.203 mag. We next estimate host galaxy stellar masses of 175 SNe. From our sample we detect a 0.039 ± 0.026 mag (1−2σ) mass-step. For reasons outlined in section 4.1.1 and 4.1.2 respectively, we increase our sBV cut to sBV > 0.8 and decrease our extinction cut to E(B −V ) ≤ 0.2 mag to see the mass step disappear entirely (0.004 ± 0.034 mag). Fast-declining SNe occur with preference in high-mass galaxies, possibly pointing to an intrinsic contribution to this mass step [22]. As NIR data is seen to significantly reduce the 3−4σ [14] mass-step detected with optical data, it is concluded that extinction likely plays a large role in the mass-step, as proposed in Brout & Scolnic 2020 [2].Presentation given over zoom due to the COVID-19 crisis.