The Kinematically Measured Pattern Speeds of NGC 2523 and NGC 4245

The purpose of this project is to observationally determine the bar pattern speeds (?[P]) of a mid-to-late type spiral and a unique SB0 galaxy as well as evaluate the galaxies' dark halo contributions to the inner disk regions. This was done by applying the method developed by Tremaine and Weinberg (1984, hereafter TW) to the SB(r)bc galaxy NGC 2523 and the SB(r)0/a galaxy NGC 4245. Determining ?[P] via the TW method requires knowledge of a galaxy's inclination as well as the luminosity weighted mean velocities and positions along a slit positioned parallel to the galaxy major axis. The galaxies were selected based on their unique resonance features, accessibility, inclination, and preferential orientation of the bar axis to the galaxy major axis. We used the RC spectrograph on the KPNO Mayall 4 meter telescope to observe the Calcium Triplet lines of the sample. The slit was positioned along the major axis of each galaxy as well as offset parallel to the major axis, through the ends of the bars. Additional observations of the K-giant stars HD 106278 and HD 109281 served as velocity standards. Assuming an inclination of 53° and a distance of 49.5 Mpc, ?[P] of NGC 2523 is 26.7 ± 2.1 km s^-1 kpc^-1. ?[P] of NGC 4245 is 53.5 ± 19.3 km s^-1 kpc^-1, assuming an inclination of 35.4° and a distance of 12.7 Mpc. The ratio of the corotation radius to the bar radius of NGC 2523 and NGC 4245 is 1.1 ± 0.1 and 1.3 ± 0.5, respectively. For a ratio that falls between 1.0 and 1.4, the bar is dubbed fast and the dark matter halo does not dominate the center of the galaxy. A self-consistent bar cannot exist if the ratio is less than 1.0. NGC 4245 is the first SB0 galaxy with strong gaseous resonance rings to have its ?[P] determined using the TW method. This is also the first documented attempt at determining ?[P] through the TW method by using the entire Calcium Triplet in the long-slit observations. This is analogous to previous studies that used the MgI b lines. Some pros and cons of observing the Calcium Triplet in such a manner are discussed. This work was supported by NSF Grant AST 050-7140 to U. of Alabama.