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Date and Time of the Query: 2019-05-23 T15:31:06 PDT
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For refcode 2003AJ....125.1261D:
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2003AJ....125.1261D DEEP HUBBLE SPACE TELESCOPE IMAGING OF SEXTANS A. II. CEPHEIDS AND DISTANCE ANDREW E. DOLPHIN AND A. SAHA Kitt Peak National Observatory, National Optical Astronomy Observatory, P.O. Box 26372, Tucson, AZ 85726; dolphin@noao.edu, saha@noao.edu EVAN D. SKILLMAN AND R. C. DOHM-PALMER Department of Astronomy, University of Minnesota, Minneapolis, MN 55455; skillman@astro.umn.edu, rdpalmer@astro.umn.edu ELINE TOLSTOY AND A. A. COLE Kapteyn Institute, University of Groningen, Postbus 800, NL-9700 AV Groningen, Netherlands; etolstoy@astro.rug.nl, cole@astro.rug.nl J. S. GALLAGHER AND J. G. HOESSEL University of Wisconsin, Department of Astronomy, 475 North Charter Street, Madison, WI 53706; jsg@astro.wisc.edu, hoessel@astro.wisc.edu AND MARIO MATEO University of Michigan, Department of Astronomy, 821 Dennison Building, 500 Church Street, Ann Arbor, MI 48109-1090; mateo@astro.lsa.umich.edu Received 2002 November 1; accepted 2002 November 19 ABSTRACT We have identified 82 short-period variable stars in Sextans A from deep Wide Field Planetary Camera 2 observations. All the periodic variables appear to be short-period Cepheids, with periods as small as 0.8 days for fundamental mode Cepheids and 0.5 days for first-overtone Cepheids. These objects have been used, along with measurements of the red giant branch (RGB) tip and red clump, to measure a true distance modulus to Sextans A of {mu}_0_ = 25.61 +/- 0.07, corresponding to a distance of d = 1.32 +/- 0.04 Mpc. Comparing distances calculated by these techniques, we find that short-period Cepheids (P < 2 days) are accurate distance indicators for objects at or below the metallicity of the Small Magellanic Cloud. As these objects are quite numerous in low-metallicity star-forming galaxies, they have the potential for providing extremely precise distances throughout the Local Group. We have also compared the relative distances produced by other distance indicators. We conclude that calibrations of RR Lyrae stars, the RGB tip, and the red clump are self-consistent, but that there appears to be a small dependence of long-period Cepheid distances on metallicity. Finally, we present relative distances of Sextans A, Leo A, IC 1613, and the Magellanic Clouds. Key words: Cepheids - galaxies: distances and redshifts - galaxies: individual (Sextans A) - Local Group
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