2008/05/12 by G. Bono, F. Caputo, G. Fiorentino +2
Physics and Astronomy · #Astronomy #Astrophysics #Astrophysics and Star Formation Studies #Cepheid variable #Cosmic distance ladder #Galaxies: Formation, Evolution, Phenomena #Galaxy #Luminosity #Metallicity #Milky Way #Physics #Redshift #Spiral galaxy #Stars #Stellar, planetary, and galactic studies #astro-ph
paper · pdf · doi:10.1086/589965
accepted for publication on ApJ
arxiv created 2008/05/12 · openalex publication_date 2008/08/26 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
We perform a detailed analysis of Cepheids in NGC 4258, the Magellanic Clouds, and Milky Way in order to verify the reliability of the theoretical scenario based on a large set of nonlinear convective pulsation models. We derive Wesenheit functions from the synthetic BVI magnitudes of the pulsators, and we show that the sign and the extent of the metallicity effect on the predicted period-Wesenheit ( P − W ) relations change according to the adopted passbands. These P − W relations are applied to measured BVI magnitudes of NGC 4258, Magellanic, and Galactic Cepheids available in the literature. We find that Magellanic and Galactic Cepheids agree with the metallicity dependence of the predicted P − W relations. Concerning the NGC 4258 Cepheids, the results strongly depend on the adopted metallicity gradient across the galactic disk. The most recent nebular oxygen abundances support a shallower gradient and provide a metallicity dependence that agrees well with current pulsation predictions. Moreover, the comparison of Cepheid distances based on VI magnitudes with distance estimates based on the revised TRGB method for external galaxies, on the HST trigonometric parallaxes for Galactic Cepheids, and on eclipsing binaries in the Magellanic Clouds seems to favor the metallicity correction predicted by pulsation models. The sign and the extent of the metallicity dependence of the P − W and of the period-luminosity ( P − L ) relations change according to the adopted passbands. Therefore, distances based on different methods and/or bands should not be averaged. The use of extragalactic Cepheids to constrain the metallicity effect requires new accurate and extensive nebular oxygen measurements.