Uncertainties in The Interstellar Extinction Curve and the Cepheid Distance to M101

Abstract

I revisit the Cepheid-distance determination to the nearby spiral galaxy M101 (Pinwheel Galaxy) of Shappee & Stanek (2011), in light of several recent investigations questioning the shape of the interstellar extinction curve at $\lambda \approx 8,000$ Å(i.e. I-band). I find that the relatively steep extinction ratio $A_I/E(V-I)=1.1450$ (Fitzpatrick & Massa 2007) is slightly favoured relative to $A_I/E(V-I)=1.2899$ (Fitzpatrick 1999) and significantly favoured relative the historically canonical value of $A_I/E(V-I)=1.4695$ (Cardelli et al. 1989). The steeper extinction curves, with lower values of $A_I/E(V-I)$, yield fits with reduced scatter, metallicity-dependences to the dereddened Cepheid luminosities that are closer to values inferred in the local group, and that are less sensitive to the choice of reddening cut imposed in the sample selection. The increase in distance modulus to M101 when using the preferred extinction curve is $\Delta \mu \sim 0.06$ mag, resulting in an estimate of the distance modulus to M101 relative to the LMC of $\Delta {\mu }_{\mathrm{LMC}}\approx 10.72\pm 0.03$ (stat). The best-fit metallicity-dependence is $d{M}_I/d[O/H]\approx (-0.38\pm 0.14$ (stat)) mag dex${}^{-1}$.

6 pages, 2 figures, 4 tables. Accepted for publication in Monthly Notices of the Royal Astronomical Society Main Journal

References in corpus (3)

• An Analysis of the Shapes of Interstellar Extinction Curves. V. The IR-Through-UV Curve Morphology
• A new Cepheid distance to the maser-host galaxy NGC 4258 and its implications for the Hubble Constant
• The Panchromatic Hubble Andromeda Treasury. VII. The Steep Mid-Ultraviolet to Near-Infrared Extinction Curve in the Central 200 pc of the M31 Bulge

Cited by in corpus (4)

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• The Metallicity Dependence of the High-Mass X-ray Binary Luminosity Function
• The Mira Distance to M101 and a 4% Measurement of H0
• The Extinction Properties of and Distance to the Highly Reddened Type Ia Supernova SN 2012cu