Statistics – Methodology
Scientific paper
Dec 2007
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2007aas...211.6902w&link_type=abstract
American Astronomical Society, AAS Meeting #211, #69.02; Bulletin of the American Astronomical Society, Vol. 39, p.859
Statistics
Methodology
Scientific paper
We have measured the disk stellar velocity ellipsoids in a subset of spiral galaxies observed for the Disk-Mass Survey, which provide information on disk stability and secular heating mechanisms. Our methodology invokes our 2D ionized gas and stellar kinematics and a suite of dynamical assumptions based on the Jeans' equations. When combined with orthogonal axes from our 2D data, either the epicycle approximation (EA) or asymmetric drift (AD) equation may close the necessary equation set, individually. We have isolated large observational and inherent systematic effects via EA-only, AD-only, and EA+AD ellipsoid decomposition methodologies. In an attempt to minimize these effects and generate robust ellipsoid measurements we explore constraints provided by higher order expansions of the Jeans' equations and direct orbital integrations. We compare our best ellipsoid axial ratio estimates to similar measurements made by, e.g., van der Kruit & de Grijs (1999, A&A, 352, 129) and Shapiro et al. (2003, AJ, 126, 2707). Finally, we discuss possibilities for the measurement of vertical velocity dispersions in low-surface-brightness galaxies by applying the characterization of the stellar velocity ellipsoid in late-type galaxies. This work is supported by the National Science Foundation (AST-0607516).
Andersen David R.
Bershady Matthew A.
Swaters Rob A.
Verheijen Marc A. W.
Westfall Kyle B.
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