  A catalog of 232 apparently interacting galaxy pairs of the M51 class is
presented. Catalog members were identified from visual inspection of mult-band
images in the IRSA archive. The major findings in the compilation of this
catalog are (1) A surprisingly low number of the main galaxies in M51 systems
are early type spirals and barred spirals. (2) Over 70% of the main galaxies in
M51 systems are 2-armed spirals. (3) Some systems that were classified as M51
types in previous studies are not M51 types as defined in this catalog. There
were a number of systems previously classified as M51 systems for which the
companion is identified as an HII region within the main galaxy or a foreground
star within the Milky Way. (4) It was found that only 18% of the M51 type
companions have redshift measurements in the literature. There is a significant
need for spectroscopic study of the companions in order to improve the value of
the catalog as a sample for studying the effects of M51 type interaction on
galaxy dynamics, morphology, and star formation. Further spectroscopy will also
help constrain the statistics of possible chance projections between foreground
and background galaxies in this catalog. The catalog also contains over 430
additional systems which are classified as "possible M51" systems. The reasons
for classifying certain systems as possible M51 systems are discussed.
