The Foundation Supernova Survey: Photospheric Velocity Correlations in Type Ia Supernovae

Abstract The ejecta velocities of Type Ia supernovae (SNe Ia), as measured by the Si ii λ 6355 line, have been shown to correlate with other supernova properties, including color and standardized luminosity. We investigate these results using Foundation Supernova Survey, a spectroscopic data release presented here, photometry analyzed SALT2 light-curve fitter. find that do not show significant evidence for an offset in between SNe high normal photospheric velocities, Δ c = 0.004 ± 0.015. Our analysis does redder high-velocity samples, objects from Carnegie Project, combined sample yielding 0.018 0.008. When split on velocity, also difference Hubble diagram residual, HR 0.015 0.049 mag. Intriguingly, we SN velocity information may be gleaned photometry, particularly optical bands. For high-redshift Ia, rest-frame red wavelengths will observed Nancy Grace Roman Space Telescope. are line previous work suggests host-galaxy stellar mass is correlated velocity: found nearly exclusively high-stellar-mass hosts. However, properties alone explain velocity-dependent differences colors luminosities across samples. Measuring understanding connection intrinsic explosion environments, cosmic time, important precision cosmology Ia.