Reconsidering the Effects of Local Star Formation On Type Ia Supernova
  Cosmology
  Recent studies found a correlation with $\sim$3 sigma significance between
the local star formation measured by GALEX in Type Ia supernova (SN Ia) host
galaxies and the distances or dispersions derived from these SNe. We search for
these effects by using data from recent cosmological analyses to greatly
increase the SN Ia sample; we include 179 GALEX-imaged SN Ia hosts with
distances from the JLA and Pan-STARRS SN Ia cosmology samples and 157
GALEX-imaged SN Ia hosts with distances from the Riess et al. (2011) H$_0$
measurement. We find little evidence that SNe Ia in locally star-forming
environments are fainter after light curve correction than SNe Ia in locally
passive environments. We find a difference of only 0.000$\pm$0.018 (stat+sys)
mag for SNe fit with SALT2 and 0.029$\pm$0.027 (stat+sys) mag for SNe fit with
MLCS2k2 (R$_V$ = 2.5), which suggests that proposed changes to recent
measurements of H$_0$ and w are not significant and numerically smaller than
the parameter measurement uncertainties. We find the greatly reduced
significance of these distance modulus differences compared to Rigault et al.
(2013) and Rigault et al. (2015) result from two improvements with fairly equal
effects, our larger sample size and the use of JLA and Riess et al. (2011)
sample selection criteria. Without these improvements, we recover the results
of Rigault et al. (2015). We find that both populations have more similar
dispersion in distance than found by Rigault et al. (2013), Rigault et al.
(2015), and Kelly et al. (2015), with slightly smaller dispersion for locally
passive SNe Ia fit with MLCS, the opposite of the effect seen by Rigault et al.
(2015) and Kelly et al. (2015). We caution that measuring local SNe Ia
environments in the future may require a higher-resolution instrument than
GALEX and that SN sample selection has a significant effect on local star
formation biases.
