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An application of Bayesian statistics to the extragalactic Cepheid distance scale

Published online by Cambridge University Press:  12 April 2016

Thomas G. Barnes III ,
Thomas J. Moffett ,
W.H. Jefferys  and
Amy D. Forestell
Thomas G. Barnes III
Affiliation:
The University of Texas at Austin, McDonald Observatory, 1 University Station, C1402, Austin, TX 78712-0259, USA
Thomas J. Moffett
Affiliation:
Purdue University, Physics Department, 1396 Physics Bldg., West Lafayette, IN 47907-1396, USA
W.H. Jefferys
Affiliation:
The University of Texas at Austin, Department of Astronomy, 1 University Station, C1400, Austin, TX 78712-0259, USA
Amy D. Forestell
Affiliation:
The University of Texas at Austin, Department of Astronomy, 1 University Station, C1400, Austin, TX 78712-0259, USA

Abstract

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We have determined quasi-geometric distances to the Magellanic Clouds, M31 and M33. Our analysis uses a Bayesian statistical method to provide mathematically rigorous and objective solutions for individual Cepheids. We combine the individual distances with a hierarchical Bayesian model to determine the galactic distances. We obtain distance moduli 18.87 ± 0.07 mag (LMC, 12 stars), 19.14 ± 0.10 (SMC, 8 stars), 23.83 ± 0.35 mag (M33, 1 star) and 25.2 ± 0.6 mag (M31, 1 star) – all uncorrected for metallicity. The M31 and M33 distances are very preliminary. If the PL relations of the LMC, SMC and Galaxy are identical, our results exclude the metallicity effect in the V, (V – R) surface brightness method predicted by Hindsley & Bell (1989) at the 5σ level. Alternately, if Hindsley & Bell’s prediction is adopted as true, we find a metallicity effect intrinsic to the Cepheid PL relation requiring a correction Δ(V – Mv) = (0.36 ± 0.07)Δ[A/H] mag. The latter has the opposite sign to other observational estimates of the Cepheid metallicity effect.

Type
Part 2. What variable stars tell us about the Local Group, including the distance scale
Information
International Astronomical Union Colloquium , Volume 193: Variable Stars in the Local Group , 2004 , pp. 95 - 98
Copyright
Copyright © Astronomical Society of the Pacific 2004

References

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