Phase Space Structure in the Solar Neighbourhood

Details Phase Space Structure in the Solar Neighbourhood Phase Space Structure in the Solar Neighbourhood

Jun 2006

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2006dda....37.0604c&link_type=abstract

American Astronomical Society, DDA meeting #37, #6.04; Bulletin of the American Astronomical Society, Vol. 38, p.669

Astronomy and Astrophysics

Astronomy

Scientific paper

This work is an attempt to model the local phase space structure of the disk of our Galaxy, as sculpted by the central bar and a tightly wound, 4-armed outer spiral pattern, that are invoked to perturb a warm quasi-exponential model galactic disk. The recovered velocity distributions are compared to the velocity diagram obtained from the Hipparcos observations. Particular emphasis is given to the the reproduction of the moving groups that have been identified in the solar neighborhood. Sample distributions will be presented to
illustrate the success of the "good" models. Besides, we will discuss the formulation of a goodness of fit analysis that checks the likelihood that the observed data is drawn from a model distribution; this is performed in terms of the p-value of a test statistic. Distributions of this goodness of fit parameter, over the studied range of radius and azimuth will be presented for each distinct
simulation: bar only; spiral only; bar and spiral, with varying ratios between their pattern speeds. The locations within this range that correspond to the "good" models are identified with the aim of extracting important dynamical quantities, namely the bar angle and pattern speed. It is found that while this approach is a neat way of estimating the bar parameters, it fails in the case when the spiral pattern is used alone, or when the pattern speeds are chosen to render the ILR of the spiral coincident with the physical location of the OLR of the bar. The dynamical origin of this behaviour and its implications will be discussed. A brief discussion of the orbits in the case of the bar-only and spiral-only perturbations will also be included. I wish to acknowledge the support of a Royal Society Dorothy Hodgkin Research Fellowship.

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