Near-Infrared and Optical Morphology of the Dusty Galaxy NGC 972

Near infrared (NIR) and optical surface photometric analyses of the dustygalaxy NGC972 are presented. The photometric profiles in the BVRJHK bands canbe fitted with a combination of gaussian and exponential profiles,corresponding to a starburst nucleus and a stellar disk respectively. Theexponential scale length in the B-band is 2.8 times larger than in the K-band,which implies a central B-band optical depth as high as 11. A bulge is absenteven in the NIR bands and hence the galaxy must be of a morphological typelater than the usually adopted Sb type. Relatively low rotational velocity andhigh gas content also favor a later type, probably Sd, for the galaxy. Only onearm can be traced in the distribution of old stars; the second arm, however,can be traced in the distribution of dust and HII regions. Data suggest a shortNIR bar, which ends inside the nuclear ring. The slowly rising nature of therotation curve rules out a resonance origin of the the nuclear ring. The ringis most likely not in the plane of the galaxy, given its circular appearance inspite of the moderately high inclination of the galaxy. The off-planar natureof the star forming ring, the unusually high fraction (30%) of the total massin molecular form, the presence of a nuclear starburst and the asymmetry ofspiral arms, are probably the result of a merger with a gas-rich companiongalaxy.Comment: Uses aas2pp4.sty and epsfig.sty, 12 pages To appear in Astronomical Journal, October 199