A Catalogue of M51 type Galaxy Associations

TL;DR

This paper presents a catalog of 232 M51-type galaxy pairs identified through visual inspection, highlighting their morphological features, classification challenges, and the need for spectroscopic follow-up to enhance understanding of galaxy interactions.

Contribution

The study provides a new, visually-compiled catalog of M51 galaxy pairs with detailed classifications and discusses the limitations and future spectroscopic needs for better analysis.

Findings

Most M51 systems have late-type, two-armed spiral galaxies.

Many previously classified M51 systems are misclassified or contain foreground objects.

Only 18% of companions have redshift data, indicating a need for spectroscopic follow-up.

Abstract

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.