Submillimeter Emission from Type Ia Supernova Host Galaxies at z = 0.5

Abstract

We present deep submillimeter observations of 17 galaxies at z=0.5 that are hosts of a Type Ia supernova. Two galaxies are detected directly, and the sample is detected statistically with a mean 850 μm flux of 1.01+/-0.33 mJy, which is 25%-135% higher than locally. We infer that the mean value of A_V in normal galaxies at z=0.5 is comparable to or greater than the mean A_V in local normal galaxies, in agreement with galaxy chemical evolution models and indirect observational evidence. Scaling from the local value given by Rowan-Robinson gives a mean extinction at z=0.5 of <A_V>=0.56+/-0.17. The dust in the brightest submillimeter object in our sample is best interpreted as normal ``cirrus'' dust similar to that seen locally. The detection rate of our sample suggests that some sources found in blank-field submillimeter surveys may not be high-redshift starbursts, but rather cirrus galaxies at moderate redshifts and with lower star formation rates. Finally, an increase in host dust extinction with increasing redshift may impact the cosmological results from distant supernova searches. This emphasizes the need to carefully monitor dust extinction when using Type Ia supernovae to measure the cosmological parameters.