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Supernovae type Ia (SNIa) are used as "standard candles" for cosmologicaldistance scales. To fit their light curve shape -- absolute luminosityrelation, one needs to assume an intrinsic color and a likelihood of hostgalaxy extinction or a convolution of these, a color distribution prior. Thehost galaxy extinction prior is typically assumed to be an exponential drop-offfor the current supernova programs ($P(A_V) \propto e^{-A_V/\tau_0}$). Weexplore the validity of this prior using the distribution of extinction valuesinferred when two galaxies accidentally overlap (an occulting galaxy pair). Wecorrect the supernova luminosity distances from the SDSS-III Supernova projects(SDSS-SN) by matching the host galaxies to one of three templates fromocculting galaxy pairs based on the host galaxy mass and the $A_V$-bias -prior-scale ($\tau_0$) relation from Jha et al. (2007).  We find that introducing an $A_V$ prior that depends on host mass results inlowered luminosity distances for the SDSS-SN on average but it does not reducethe scatter in individual measurements. This points, in our view, to the needfor many more occulting galaxy templates to match to SNIa host galaxies to ruleout this possible source of scatter in the SNIa distance measurements. We matchocculting galaxy templates based on both mass and projected radius and we findthat one should match by stellar mass first with radius as a secondaryconsideration. We discuss the caveats of the current approach and our aim is toconvince the reader that a library of occulting galaxy pairs observed with HSTwill provide sufficient priors to improve (optical) SNIa measurements to thenext required accuracy in Cosmology.

The Dependence of the $A_V$ Prior for SN\,Ia on Host Mass and Disk Inclination