RSAA Colloquia / Seminars / Feast-of-Facts: Friday, 28 November 2014, 14:00-14:20; Duffield Lecture Theatre

David Nataf

"Uncertainties in the Interstellar Extinction and the Cepheid Distance to M101"

I revisit the Cepheid-distance determination to the nearby spiral galaxy M101 (Pinwheel Galaxy), in light of several recent investigations questioning the shape of the interstellar extinction curve. I find that the (steeper) extinction curve of Fitzpatrick & Massa (2007) is slightly favoured relative to the vastly more cited curve of Cardelli et al. (1989), and this consequently increases the inferred distance modulus by ~0.06 mag. I also briefly discuss an undiagnosed and possibly significant systematic error I noticed while perusing the literature, that the assumptions of metallicity-dependence in the literature may be invalid.