Brightest Stars in Galaxies as Distance Indicators

Abstract

The current status of the absolute magnitude calibration of the brightest blue and red supergiants in galaxies of different absolute magnitudes shows trends of M(star) with M(parent galaxy). Red supergiants show a more shallow correlation than the blue stars for galaxies brighter than MB = −14. For fainter galaxies, the red supergiant method appears to become totally degenerate.Four areas of application of the brightest star data are discussed as (1) determining MB of the Eddington limit to be ∼−10 for blue supergiants, (2) calibration of MB(max) = −20.0±0.4 for type I supernovae, leading to a Hubble constant of HO = 43±10 km s−1 Mpc−1, (3) detection of the deceleration of the cosmological expansion by the Local Group leading to a Local Group mass of 4×1011 M⊙ and a mass-to-blue light ratio of 3, and (4) use of the brightest stars to map the Virgo cluster velocity perturbation of the Hubble flow.