Structures and dynamics of NGC 3359: Observational and theoretical studies of a barred spiral galaxy

This research is a synthesis of observational and theoretical studies of the barred spiral galaxy NGC 3359. Analysis of the observational data was combined with numerical simulations to gain a deeper understanding of the system. The galaxy is gas-rich, with the mass of H I making up about 6% of the total dynamical mass. The distribution of the material is globally symmetric about the center. Atomic hydrogen gas call be detected out as far as 24 kpc from the center (or approximately twice the length of the photometric disk-scale length). The galaxy has a grand design appearance with two spiral arms of similar pitch angles extending from the ends of the stellar bar. Along these structures reside most of the bright, giant H II regions of the galaxy. Two additional, purely H I gas arms also exist outside the optical disk. The nucleus of the galaxy is strongly covered in dust and contains little CO or Hα emission. Although dust complexes are present within the bar region, they appear as dusty patches rather than the classical dust lanes. Radio continuum emission appears to be centrally concentrated and thermally induced, as it is detected predominantly around the brightest H II regions located within the bar. Analysis of the near-infrared and optical images of the galaxy have shown that, as the wavelength of observation increases, the disk scale length also increases; while the bar position angle decreases.; Kinematical study of 21-cm and Hα velocity fields show that the gases are circularly rotating. However, near the bar and spiral arms of the galaxy, strong; streaming motions as large as 50 km s−1 have been detected. Evidence also exists for out-of-plane motions near the brightest H II regions Such types of gas flow kelp to explain the curious double peak feature of the H I rotation curve.; Numerical simulations of stellar orbits and gas flow within the disk of the galaxy have yielded the fascinating and rare result that the system has two pattern speeds. To reproduce the proper stellar orbits that build and support the observed bar structure, a pattern speed of 39.17 km s −1 kpc−1 is required. To match the pitch angles of the spiral arms with the SPH simulations, slower pattern speeds (between 10.00 and 15.52 kms−1 kpc−1) were used. The observed density distribution and kinematical results are also best reproduced by the lower-pattern-speed models.