An Alternate Calculation of the Distance to M87 Using the Whitmore et al. Luminosity Function for Its Globular Clusters: [ITAL]H[/ITAL][TINF]0[/TINF] Therefrom

Abstract

An alternate calculation to that made by Whitmore et al. (WSLMB) is set out for the distance to M87 using their globular cluster luminosity function (GCLF) for M87 in the Virgo Cluster. They have concluded from these data that H0 = 78 ± 11 km s-1 Mpc-1. Our purpose is to show how a different set of precepts leads to a substantially smaller value of H0 that is in statistical agreement with other analyses that favor the long distance scale. Adopting the WSLMB observed turnover apparent magnitude for the GCLF of V = 23.79 ± 0.2 (external), together with AV = 0.00 mag for the foreground Galactic absorption, and MV0 = -7.62 ± 0.2 (external) as the calibration of the turnover luminosity gives (m - M)0 = 31.41 ± 0.28 for the distance modulus of M87. Using the cosmic velocity of the E galaxy Virgo core as v(cosmic) = 1179 ± 17 km s-1 gives H0 = 62 ± 9 km s-1 Mpc-1. The procedure of WSLMB and others in stepping a Virgo distance to the Coma Cluster and then using a Coma velocity that still contains a random component to determine H0 is argued. The cosmic velocity for Virgo, calculated by reading a Hubble diagram of relative distances of 17 remote clusters versus cosmic microwave background velocities at zero modulus difference to Virgo (Jerjen & Tammann), overcomes this error by circumventing the problem of accounting for any random and/or streaming motions of the Virgo Cluster and/or of the Coma Cluster about the ideal Hubble flow. This procedure cuts to the core of the distance scale problem, eliminating the major uncertainty concerning local random motions. Four sources of possible systematic errors in the Virgo Cluster modulus using the GCLF method, as applied to M87, are also set out, suggesting that the value of H0 = 62 is an upper limit.