Gravitational lens time delays for distant supernovae: Breaking the degeneracy between radial mass profiles and the Hubble constant

Abstract

Any attempt to measure the Hubble constant with gravitational lens time delays is often limited by the strong degeneracy between radial mass profiles of lens galaxies and the Hubble constant. We show that strong gravitational lensing of Type Ia supernovae breaks this degeneracy; the standard candle nature of the Type Ia supernova luminosity function allows one to measure the magnification factor directly, and this information is essential to constrain radial mass profiles and the Hubble constant separately. Our numerical simulation demonstrates that the Hubble constant can be determined with ∼5 per cent accuracy from several lens events only if magnification factors are used as constraints. Therefore, a distant supernova survey is a promising way to measure the global Hubble constant independently with the local estimates.