PI: Patrick Kelly, Stanford University, firstname.lastname@example.org
Address: Physics Department, 382 Via Pueblo Mall, Stanford, CA 94305, USA
CoI: David Burke, SLAC National Accelerator Laboratory
CoI: Anja von der Linden, Stanford University
Title: Shifting Standards: SN Ia Calibration Across Host Environments
Abstract: We propose observations of 72 SN Ia host galaxies to expand the number of low-redshift SN with host \textitu'\textitg'\textitr'\textiti'\textitz' photometry in the Constitution sample to ~150, including existing data from the SDSS. Host stellar masses estimated from SDSS imaging reveal a systematic trend in Hubble residuals where SN Ia are ~10% brighter (after light curve correction) when they occur in more massive galaxies. This effect exists in residuals from the MLCS2k2 (R_V=1.7 and R_V=3.1), SALT, and SALT2 light curve fitters even after marginalizing over systematic trends with light curve parameters. If the SN Ia width-color-luminosity relation varies with environment, current SN Ia cosmological results may contain systematic error and future efforts will need to carefully account for the effect. The proposed observations will place strong constraints on a host mass- dependent trend in Hubble residuals.
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