Predicted circular velocity as a function of radius, for a galaxy of similar size and mass to the Milky Way and that is influenced by a cosmological constant. The displayed rotation curves are for increasing magnitudes of a positive (in blue) and a negative (in red) cosmological constant. The Keplerian curve with Λ = 0 is also shown (in black). Whereas a positive cosmological constant steepens the decline of a rotation curve, a negative cosmological constant flattens the rotation curve, causing a steady increase at larger galactic radii. Solid body rotation in the centre of the galaxy is not shown.