M31’s Radial Velocity

For M31, Wikipedia gave the following:  M31’s Radial Velocity: The Andromeda Galaxy (M31) is moving toward us with a radial speed of roughly 300 km/s. (Sometimes you’ll see a value around –300 km/s; the negative sign indicates an approach.) For our calculation, we’re interested in the magnitude of the shift, so we’ll use 300 km/s.

  Rest frequency:          1420.41 MHz
            |
          Δf ≈ 1.42 MHz (blueshift)
            |
   Observed frequency:      ~1421.83 MHz

Keep in mind though that -300km/s is the average radial velocity of M31. The edges add or subtract ~200 some odd km/s from that value due to rotation of the galaxy itself. It has a peak around -75 km/s and another peak around -520 km/s.