SNIa observed in H-band combined with UV-opt. LCs

We find that SNeIa in galaxies more massive than 10^10.43^M_{sun}_ are 0.13+/-0.04mag brighter in H than SNe Ia in less massive galaxies. The same set of SNe Ia observed at optical wavelengths, after width-color-luminosity corrections, exhibit a 0.10+/-0.03mag offset in the Hubble residuals.

We observe an outlier population (|{Delta}H_max_|>0.5mag) in the H band and show that removing the outlier population moves the mass threshold to 10^10.65^M_{sun}_ and reduces the step in H band to 0.08+/-0.04mag, but the equivalent optical mass step is increased to 0.13+/-0.04mag. We conclude that the outliers do not drive the brightness-host-mass correlation. Less massive galaxies preferentially host more higher-stretch SNe Ia, which are intrinsically brighter and bluer.