![]() ![]() 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. Calibrated contour maps and integrated luminosities of the system are presented.The maximum detected extent of the system is 40 arcmin or 120kpc. Deep, integrated photographic plates (IIIa-J) also show the large, structured outer regions and the complex nature of the more » region between the two galaxies. The I data in particular show the broad spiral features first shown photographically by Zwicky. Colors and magnitudes of the spiral arms are presented. These data indicate the complexity and the very large extent of the system. 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. ![]() Photoelectric and photographic data are presented for the two components of the M51 system, NGC 5194 and NGC 5195. Extant simulations of M51 have difficulty matching both the wealth of tidal structure in the system and the lack of stars in the H i tail, motivating new modeling campaigns to study the dynamical evolution of this classic interacting system. Finally, we confirm the strong segregation of gas and stars in the southeast tail and do not detect any diffuse stellar component in the H i portion of the tail. The northwest plume’s morphology and red color (B−V=0.8) instead argue that it originated from tidal stripping of M51a’s extreme outer disk. We also trace the extremely diffuse northwest plume out to a total extent of 20′ (43 kpc) from NGC 5194 (M51a) and show it to be physically distinct from the overlapping bright tidal streams from M51b. While the northeast plume may be a faint outer extension of the tidal more » “crown” north of NGC 5195 (M51b), the south plume has no analog in any existing M51 simulation and may represent a distinct tidal stream or disrupted dwarf galaxy. Three regions of spiral structure in M51 are proposed: (1) the extended tidal arm created by the previous passage of NGC 5195 (2) the strong tidal arms seen in the optical and created by the most recent passage 70 to 84 million years ago and (3) more » the inner density wave excited by these tidal arms. The inner structure is consistent with resonantly excited m = 2 Lindblad dispersion orbits. The transition between the directly excited outer tidal arms and the indirectly excited inner arms explains the symmetrically placed bends in the outer arms of M51. The outer arms of M51 behave like material arms inward to approx. ![]() This method is suitable for nearly face-on grand design galaxies with companions. An analytic method was developed to set limits to some of the orbit parameters. A simple gas cloud collision algorithm was included that permits features in the gas particles to strengthen. The problem reduces to choosing a finite set of orbits (for NGC 5195) that can model the observed features of M51. The grand design spiral galaxy M51 (NGC 5194) was modeled as an interacting system and a three component self-gravitating N-body code was used to simulate the gravitational interaction. ![]()
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