Dark Matter Around the Local Group?

Extract

The Hubble expansion rate measured in the short distance scale varies from 70–75 to 90 km s⁻¹ Mpc⁻¹ as the kinematic distance (corrected for in fall velocity toward Virgo) increases from D_v = 200–400 km s⁻¹ to D_v ∼ 1300 km s⁻¹. It should be observed in the long scale as well (starting from a lower value), if the same methods were used in the same way. The Malmquist bias for spiral galaxies in the range D_v ≤ 1300 km s⁻¹ is very small or null. The velocity distribution of galaxies in the nearest groups compared with models of various rms velocity dispersions, suggests that at small distance, dispersions of 100 km s⁻¹ or more do not fit the observations. The effect of the deceleration due to the mass of the Local Group on the very nearby velocity field is negligible beyond 2.5–3 Mpc. The low local value of H_o extends approximately over ∼ 6–7 Mpc.