Clustering of Local Group Distances: Publication Bias or Correlated Measurements? VII. A Distance Framework out to 100 Mpc

Abstract

We consider the body of published distance moduli to the Fornax and Coma galaxy clusters, with specific emphasis on the period since 1990. We have carefully homogenized our final catalogs of distance moduli onto the distance scale established in the previous papers in this series. We assessed systematic differences associated with the use of specific tracers and consequently discarded results based on application of the Tully–Fisher relation and of globular cluster and planetary nebula luminosity functions. We recommend “best” weighted relative distance moduli for the Fornax and Coma clusters with respect to the Virgo cluster benchmark of mag and mag. The set of weighted mean distance moduli (distances) we derived as most representative of the clusters’ distances is m − M 0 F o r n a x = 31.41 ± 0.15 m a g ( D = 19.1 − 1.2 + 1.4 M p c ) a n d = 31.21 ± 0.28 m a g ( D = 17.5 − 2.2 + 2.4 M p c ) , m − M 0 C o m a = 34.99 ± 0.38 m a g ( D = 99.5 − 15.9 + 19.0 M p c ) a n d = 34.78 ± 0.27 m a g ( D = 90.4 − 10.6 + 11.9 M p c ) , where the first distance modulus for each cluster is the result of our analysis of the direct, absolute distance moduli, while the second modulus is based on distance moduli relative to the Virgo cluster. While the absolute and relative distance moduli for both clusters are mutually consistent within the uncertainties, the relative distance moduli yield shorter absolute distances by ∼1 σ . It is unclear what may have caused this small difference for both clusters; lingering uncertainties in the underlying absolute distance scale appear to have given rise to a systematic uncertainty of the order of 0.20 mag.