Journal Article

The effect of metallicity on Cepheid magnitudes and the distance to M33*

V. Scowcroft, D. Bersier, J. R. Mould and P. R. Wood

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 396, issue 3, pages 1287-1296
Published in print July 2009 | ISSN: 0035-8711
Published online June 2009 | e-ISSN: 1365-2966 | DOI: http://dx.doi.org/10.1111/j.1365-2966.2009.14822.x
The effect of metallicity on Cepheid magnitudes and the distance to M33*

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We present the results from a multi–epoch survey of two regions of M33 using the 3.5–m Wisconsin–Indiana–Yale–NOAO (WIYN) telescope. The inner field is located close to the centre of the galaxy, with the outer region situated about 5.1 kpc away in the southern spiral arm, allowing us to sample a large metallicity range. We have data for 167 fundamental mode Cepheids in the two regions. The reddening–free Wesenheit magnitude Wvi period–luminosity (PL) relations were used to establish the distance modulus of each region, with μinner= 24.37 ± 0.02 mag and μouter= 24.54 ± 0.03 mag. The apparent discrepancy between these two results can be explained by the significant metallicity gradient of the galaxy. We determine a value for the metallicity parameter of the PL relation =−0.29 ± 0.11 mag dex−1, consistent with previous measurements. This leads to a metallicity corrected distance modulus to M33 of μγ= 24.53 ± 0.11 mag.

Keywords: catalogues; Cepheids; galaxies: distances and redshifts; galaxies: individual: M33

Journal Article.  7142 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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