Observational Disk Dynamics of Late-Type Galaxies

(Abridged) The primary concern of this thesis is the measurement of the stellar velocity ellipsoid (SVE) in galaxy disks. While a few attempts exist in the literature, we know of no study providing as detailed a discussion of the empirical procedure nor of the associated errors in SVE measurements as that presented herein. This is despite the relevance of the SVE to galaxy-disk dynamics as it quantifies, in gross terms, the stellar phase-space distribution function, but largely due to the observational expense of the measurement. We address the observational obstacles by using the WIYN SparsePak integral-field unit, which is well-suited to measuring line-of-sight kinematics in the low-surface-brightness, low-velocity-dispersion regime presented by galaxy disks. Thus, we obtain ionized gas and stellar kinematics for seven galaxies and characterize the SVE using a set of six decomposition methods resulting from consideration of four dynamical relations pulled from the literature and theories of galactic dynamics. These analyses have resulted in the following conclusions: (1) We find general agreement with the results of previous SVE studies; however, we do not confirm a cold-to-hot progression of "disk temperature'' from late- to early-type (Sa) galaxies due to the dominance of different secular processes. The mean vertical-to-radial axial ratio is 0.66 for our sample. (2) Five of seven galaxies show a Toomre stability criterion of Q˜3 the others are only marginally stable with Q˜1. (3) We find indications of a nearly constant line-of-sight velocity dispersion in the extended parts of at least three galaxies, implying an increase in the mass-to-light ratio by factors of a few at these radii. We acknowledge support from the NSF (AST-9970780, AST-0307417, AST-0607516), UW Graduate School (PRJ13SL, 050167, and the Vilas Associate award), and NASA/JPL/Spitzer (GO-30894). KBW is currently supported by an NSF International Research Fellowship (OISE-0754437).