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The velocity-metallicity relation is the correlation between low metallicity and high velocity dispersion within the local Milky Way. These also have a relation with age (thus, the age-velocity-metallicity relation, AVMR): lower metallicity is associated with older stars that formed before supernovae increased the metallicity of molecular clouds.
The velocity-metallicity relation can be demonstrated by peculiar velocity diagrams of a chosen group of stars of some given spectral types, that plot the peculiar velocity components based on the neighborhood of the given stars: one component radial to the galaxy and the other component perpendicular to the first, within the galactic plane. This reveals two populations, that show a correlation with metallicity of the individual stars.
A velocity-metallicity correlation has also been found among high-redshift galaxies: a galaxy's overall stellar velocity indicated by line broadening is correlated with the galaxy's overall metallicity.