On the Source of the Dust Extinction in Type Ia Supernovae

Wednesday, 20 August 2014 9 a.m. — 10 a.m. MST

AURA Lecture Hall

NOIRLab South Colloquia
MARK PHILLIPS (Associate Director for Magellan Carnegie Institution of Washington, Las Campanas Observatory and NOAO South Visiting Astronomer)

Echelle observations can be used as an independent means of probing the dust extinction of SNe Ia. I show that the extinction of the objects where the diffuse interstellar band at 5780 Angstroms is detected is consistent with the visual extinction derived from the supernova colors. This strongly suggests that the dust is predominantly located in the interstellar medium of the host galaxies and not in circumstellar material associated with the progenitor system. However, the echelle spectra also reveal that one quarter of the supernovae display anomalously large Na I column densities in comparison to the amount of dust extinction derived from their colors. Remarkably, all of the cases of unusually strong Na I D absorption correspond to ÒBlueshiftedÓ profiles in the classification scheme of Sternberg et al. (2011). This coincidence suggests that outflowing circumstellar gas may be responsible for at least some of the cases of anomalously large Na I column densities.