Photometric study of the M51 system

Photoelectric and photographic data are presented for the two components of the M51 system, NGC 5194 and NGC 5195. The photoelectric observations (UBV and I) are presented as a series of drift scans with various diaphragm sizes covering the bright central and faint outer regions. These data indicate the complexity and the very large extent of the system. Colors and magnitudes of the spiral arms are presented. The I data in particular show the broad spiral features first shown photographically by Zwicky. Deep, integrated photographic plates (IIIa-J) also show the large, structured outer regions and the complex nature of the region between the two galaxies. Calibrated contour maps and integrated luminosities of the system are presented.The maximum detected extent of the system is 40 arcmin or 120kpc. If a M/L ratio of 10 is assumed, the mass in the outer envelope is equal to the mass obtained for the more familiar bright optical components.These data and their presentation in the form of photoelectric drift scans, composite photographs, contour maps, and three-dimensional plots show the marvelous complexity of the system. It would seem that the individual galaxies, NGC 5194 and NGC 5195, cannot be considered separately but must be studied in the context of their being members of the M51 system