Clustering of Supernova Ia Host Galaxies

For the first time the cross-correlation between Type Ia supernova host galaxies and surrounding field galaxies is measured using the Supernova Legacy Survey sample. Over the z = 0.2–0.9 redshift range we find that supernova hosts are correlated an average of 60% more strongly than similarly selected field galaxies over the 3''-100'' range and about a factor of 3 more strongly below 10''. The correlation errors are empirically established with a jackknife analysis of the four SNLS fields. The hosts are more correlated than the field at a significance of 99% in the fitted amplitude and slope, with the point-by-point difference of the two correlation functions having a reduced χ² for 8 degrees of freedom of 4.3, which has a probability of random occurrence of less than 3 × 10⁻⁵. The correlation angle is 1.5'' ± 0.5'', which deprojects to a fixed comoving correlation length of approximately 6.5 ± 2 h⁻¹ Mpc . Weighting the field galaxies with the mass and star formation rate supernova frequencies of the simple A + B model produces good agreement with the observed clustering. We conclude that these supernova clustering differences are primarily the expected outcome of the dependence of supernova rates on galaxy masses and stellar populations with their clustering environment.