Local Flow

The motions of galaxies with respect to one another can be broken down into three components:

  1. The Hubble flow due to the expansion of the Universe,
  2. The motions due to the orbits of galaxies within the groups or clusters in which they reside,
  3. The local flows of the groups/clusters with respect to the Hubble flow

Local flows are the result of the gravitational effects of large-scale structures which cause galaxies to deviate from the local Hubble flow. The Local Group of galaxies (including the Milky Way) has a local flow of about 600 km/s in the direction of the constellation Centaurus. This is most convincingly demonstrated by the cosmic microwave background dipole, which shows clear evidence for a bulk motion of the Local Group in the direction of the galaxy superclusters that make up the Great Attractor.

The motions of galaxies can be broken down into three components: The Hubble flow, the local flow and motions within clusters. The combined local flow and motion-within-cluster constitute the ‘peculiar motion’

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