The infall velocity toward Virgo, the Hubble constant, and a search for motion toward the microwave background
G. Tammann, Allan Sandage
Abstract
G. Tammann, Allan Sandage
Abstract
From data on distance ratios of eight clusters and groups of galaxies in the velocity interval 800 - 2000 km s-1, the infall of the Local Group toward the Virgo Cluster center due to the overdensity of the Virgo complex is determined to be vvc = 200±50 km s-1. This gives a low value of M/LB ≈ 70 averaged over the 20 Mpc volume of the Virgo Cluster complex inside the Local Group circle and requires the local cosmic density parameter to be Ω0 = 0.09. The global value of the Hubble constant is H0 = 50±7 km s-1Mpc-1, if the distance to the Virgo Cluster is 21.6 Mpc. It scales directly with any other assumed Virgo distance. The mean random motion of galaxies about an ideal Hubble flow may increase with scale of the structure, ranging from σ(v) = 90 km s-1 for scales of ≡1 Mpc to σ(v) ≈ 500 km s-1 for scales of ≡50 Mpc.
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From data on distance ratios of eight clusters and groups of galaxies in the velocity interval 800 - 2000 km s-1, the infall of the Local Group toward the Virgo Cluster center due to the overdensity of the Virgo complex is determined to be vvc = 200±50 km s-1. This gives a low value of M/LB ≈ 70 averaged over the 20 Mpc volume of the Virgo Cluster complex inside the Local Group circle and requires the local cosmic density parameter to be Ω0 = 0.09. The global value of the Hubble constant is H0 = 50±7 km s-1Mpc-1, if the distance to the Virgo Cluster is 21.6 Mpc. It scales directly with any other assumed Virgo distance. The mean random motion of galaxies about an ideal Hubble flow may increase with scale of the structure, ranging from σ(v) = 90 km s-1 for scales of ≡1 Mpc to σ(v) ≈ 500 km s-1 for scales of ≡50 Mpc.
Key concepts: Physics, Virgo Cluster, Astrophysics, Cosmic microwave background, Galaxy, Hubble's law, Local Group, Astronomy