Browsing by Subject "period-luminosity relations"
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Item The ACS Nearby Galaxy Survey Treasury. III. Cepheids In The Outer Disk Of M81(2009-06) McCommas, Les P.; Yoachim, Peter; Williams, Benjamin F.; Dalcanton, Julianne J.; Davis, Matthew R.; Dolphin, Andrew E.; Yoachim, PeterThe ACS Nearby Galaxy Survey Treasury (ANGST) has acquired deep ACS imaging of a field in the outer disk of the large spiral galaxy M81. These data were obtained over a total of 20 Hubble Space Telescope orbits, providing a baseline long enough to reliably identify Cepheid variable stars in the field. Fundamental mode and first overtone types have been distinguished through comparative fits with corresponding Cepheid light curve templates derived from principal component analysis of confirmed Cepheids in the Large Magellanic Cloud (LMC), Small Magellanic Cloud, and Milky Way. A distance modulus of 27.78 +/- 0.05(r) +/- 0.14(s) with a corresponding distance of 3.60 +/- 0.23 Mpc has been calculated from a sample of 11 fundamental mode and two first overtone Cepheids (assuming an LMC distance modulus of mu(LMC) = 18.41 +/- 0.10(r) +/- 0.13(s)).Item The Cepheid Distance Scale: Recent Progress In Fundamental Techniques(2009-09) Barnes, T. G.; Barnes, T. G.This review examines progress on the Pop I, fundamental-mode Cepheid distance scale with emphasis on recent developments in geometric and quasi-geometric techniques for Cepheid distance determination. Specifically I examine the surface brightness method, interferometric pulsation method, and trigonometric measurements. The three techniques are found to be in excellent agreement for distance measures in the Galaxy. The velocity p-factor is of crucial importance in the first two of these methods. A comparison of recent determinations of the p-factor for Cepheids demonstrates that observational measures of p and theoretical predictions agree within their uncertainties for Galactic Cepheids.