Estimating the Luminosity Function of M51-Type Galaxies A new sample of M51-type galaxies consisting of 46 systems is used toestimate the B-band luminosity function. The luminosity function for theprimary components of the systems can be described by a Schechterfunction with the parameters * = (1.4±0.3)×10-5 Mpc-3, =-1.3+0.4 -0.3, and M * = -20.3+0.2 -0.1. The values of the latter twoparameters are comparable to those for isolated galactic pairs. Theresulting estimate of the average density of M51-type galaxies is(4±3)% of the average density of isolated pairs for luminositiesin the range -22m.0
