2023/09/19 by Madore, Barry F., Freedman, Wendy L. · 2 citations
#FOS: Physical sciences #Solar and Stellar Astrophysics (astro-ph.SR)
paper · doi:10.48550/arxiv.2309.10859
Using an updated and significantly augmented sample of Cepheid and TRGB distances to 28 nearby spiral and irregular galaxies, covering a wide range of metallicities, we have searched for evidence of a correlation of the zero-point of the Cepheid Period-Luminosity relation with HII region (gas-phase) metallicities. Our analysis, for the 21 galaxies closer than 12.5 Mpc, results in the following conclusions: (1) The zero points of the Cepheid and TRGB distance scales are in remarkably good agreement, with the mean offset in the zero points of the most nearby distance-selected sample being close to zero, Delta modo(Cepheid - TRGB) = -0.026 +\- 0.015 mag (for an I-band TRGB zero point of MI = -4.05 mag); however, for the more distant sample, there is a larger offset between the two distance scales, amounting to -0.073 +/- 0.057 mag. (2) The individual differences, about that mean, have a measured scatter of +/- 0.068~mag. (3) We find no statistically significant evidence for a metallicity dependence in the Cepheid distance scale using the reddening-free W(V,VI) period-luminosity relation: Delta modo (Cepheid - TRGB) = -0.022 (+/- 0.015) × ([O/H]-8.50) - 0.003 (+/- 0.007)