Chris B. D'Andrea, Ravi R. Gupta, Masao Sako, Matt Morris, Robert C. Nichol, Peter J. Brown, Heather Campbell, Matthew D. Olmstead, Joshua A. Frieman, Peter Garnavich, Saurabh W. Jha, Richard Kessler, Hubert Lampeitl, John Marriner, Donald P. Schneider, Mathew Smith
We examine the correlation between supernova host galaxy properties and their
residuals on the Hubble diagram. We use supernovae discovered during the Sloan
Digital Sky Survey II - Supernova Survey, and focus on objects at a redshift of
z < 0.15, where the selection effects of the survey are known to yield a
complete Type Ia supernova sample. To minimize the bias in our analysis with
respect to measured host-galaxy properties, spectra were obtained for nearly
all hosts, spanning a range in magnitude of -23 < M_r < -17. In contrast to
previous works that use photometric estimates of host mass as a proxy for
global metallicity, we analyze host-galaxy spectra to obtain gas-phase
metallicities and star-formation rates from host galaxies with active star
formation. From a final sample of ~ 40 emission-line galaxies, we find that
light-curve corrected Type Ia supernovae are ~ 0.1 magnitudes brighter in
high-metallicity hosts than in low-metallicity hosts. We also find a
significant (> 3{\sigma}) correlation between the Hubble residuals of Type Ia
supernovae and the specific star-formation rate of the host galaxy. We comment
on the importance of supernova/host-galaxy correlations as a source of
systematic bias in future deep supernova surveys.
View original:
http://arxiv.org/abs/1110.5517
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