J/ApJ/812/31 Local Star Formation effects on type Ia SNe (Jones+, 2015) ================================================================================ Reconsidering the effects of local star formation on type Ia supernova cosmology. Jones D.O., Riess A.G., Scolnic D.M. =2015ApJ...812...31J (SIMBAD/NED BibCode) ================================================================================ ADC_Keywords: Photometry, ultraviolet ; Redshifts ; Supernovae ; Magnitudes Keywords: cosmology: observations; distance scale Abstract: Recent studies found a correlation with ~3{sigma} significance between the local star formation measured by GALEX in 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 Joint Light-curve Analysis (JLA) and Pan-STARRS SN Ia cosmology samples and 157 GALEX-imaged SN Ia hosts with distances from the Riess et al. (2011, J/ApJ/730/119) 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 0.000+/-0.018 (stat+sys) mag for SNe fit with SALT2 and 0.029+/-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 measure systematic uncertainties of ~0.01-0.02mag by performing several plausible variants of our analysis. We find the greatly reduced significance of these distance modulus differences compared to Rigault et al. (2013A&A...560A..66R) results from two improvements with fairly equal effects, our larger sample size and the use of the JLA and Riess et al. sample selection criteria. Without these improvements, we recover the results of Rigault et al. We find that both populations have similar dispersions in distance than found by Rigault et al. and Kelly et al. (2015Sci...347.1459K), with slightly smaller dispersions for locally passive (log({Sigma}_SFR_)<-2.9dex) SNe Ia fit with MLCS, the opposite of the effect seen by Rigault et al. and Kelly et al. We caution that measuring the local environments of SNe Ia in the future may require a higher resolution instrument than GALEX and that SN Ia sample selection has a significant effect on local star formation biases. Description: We used two samples of SNe for this analysis, one from the R11 (Riess et al. 2011, J/ApJ/730/119) measurement of H0 and the other from the dark energy equation of state measurements of B14 (Betoule et al. 2014, J/A+A/568/A22) and Pan-STARRS (PS1; Rest et al. 2014, J/ApJ/795/44; Scolnic et al. 2014ApJ...795...45S, D. M. Scolnic et al. 2015, in preparation). These two samples rely on many of the same SNe, but R11 use the MLCS light curve fitter to perform their baseline analysis while B14 and PS1 use SALT2 (Guy et al. 2010, J/A+A/523/A7; version 2.4). File Summary: -------------------------------------------------------------------------------- FileName Lrecl Records Explanations -------------------------------------------------------------------------------- ReadMe 80 . This file table3.dat 135 336 *The LSF step sample -------------------------------------------------------------------------------- Note on table3.dat: Rigault et al. (2015ApJ...802...20R) found a mean difference in Hubble residuals between SNe Ia{epsilon} and Ia{alpha} (hereafter referred to as the LSF step) of ~0.09-0.17mag at 2-4{sigma} significance with different light curve fitters. See section 1. -------------------------------------------------------------------------------- See also: B/sn : Asiago Supernova Catalogue (Barbon et al., 1999-) J/A+A/578/A8 : Multi-resolution images of M33 (Boquien+, 2015) J/ApJ/795/44 : PS1 SNe Ia (0.023, as these are outside the isophotal radius of the host. Note (5): * = Visual inspection found that these SNe Ia were within the isophotal radius of their host. A dust correction was applied. Note (6): Cut applied to the SN as follows: Incl = SN in an inclined host; UV = SN has no GALEX images; FOV = GALEX images where the SN position is >0.55 degrees from the field center; SFR = Morphologically ambiguous SN. -------------------------------------------------------------------------------- Acknowledgments: David Jones [Johns Hopkins University] for PS1 supernovae coordinates History: From electronic version of the journal ================================================================================ (End) Prepared by [AAS], Emmanuelle Perret [CDS] 01-Feb-2016