Mathematics – Logic
Scientific paper
Aug 1980
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1980pasp...92..397p&link_type=abstract
Astronomical Society of the Pacific, Publications, vol. 92, Aug.-Sept. 1980, p. 397-408. Research supported by the University o
Mathematics
Logic
15
Astronomical Catalogs, Galactic Rotation, Galactic Structure, Interstellar Gas, Spiral Galaxies, Astrometry, Astronomical Photometry, Galactic Evolution, Kinematics, Radial Velocity
Scientific paper
From a spectroscopic investigation of the late-type galaxy NGC 4945 (de Vaucouleurs classification SB(s)cd:), we derive the following conclusions: (1) Over the major part of the optical image of the galaxy, the mean rotation curve is linear, with the center of rotation displaced 45" = 1.1 kpc northeast of the apparent optical center of the galaxy, features which are in accord with known kinematical properties of other late-type Sd or Sm galaxies. (2) On the southwest side of the galaxy, velocity data in positions offset from the major axis show strong departures from purely circular motions. This is most easily interpreted in terms of an infall of gas into the galaxy. (3) With regard to the interpretation (de Vaucouleurs 1964a) of NGC 4945 as an asymmetrical barred spiral seen nearly edge-on, there is no evidence for the outward streaming of gas along the bar which has been reported in other galaxies of similar morphological class. In addition, the observed departures from circular motion are not in agreement with those expected in the de Vaucouleurs-Freeman (1973) mass model for asymmetrical systems; thus, if a bar does exist in the galaxy, it can be only a minor perturbation in the mass distribution.
Radial velocities and photometry of 15 background galaxies in the vicinity of NGC 4945 are reported in an Appendix.
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