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Title:A kinematic and abundance survey in the galactic rotational directions
Author(s):Bell, David James
Doctoral Committee Chair(s):Yoss, Kenneth M.
Department / Program:Astronomy
Degree Granting Institution:University of Illinois at Urbana-Champaign
Subject(s):Physics, Astronomy and Astrophysics
Abstract:Photometric and spectroscopic observations have been obtained for 1028 G and K-type stars near the cardinal directions corresponding to Galactic rotation and anti-rotation. The spectra have been used to obtain radial velocities by cross-correlation, and estimates of stellar metallicity via a spectrophotometric index. The DDO and BV photometric observations yield estimates of distance, color excess, spectral type and metallicity. Reddening trends as a function of distance are found to be consistent with previous investigations in each of the two directions. An extracted subsample of 570 late-type giants has been used with maximum likelihood modeling to study the kinematic and abundance characteristics of the local Galactic disk. The data are well represented by a two-component disk model in which the "thick disk" has a mean abundance of $-0.35 \pm 0.06$, an asymmetric drift of $43 \pm 9$ km s$\sp{-1}$, and a local normalization of $13 \pm 3$%. A continuous "extended disk" model is also fitted to the data, but is found to be significantly inferior through a likelihood ratio test.
The discrete nature supports disk-formation models in which the thick disk is created by a separate distinguishable process relative to the thin disk, such as through a merger event early in the disk's history. It is less consistent with models in which the thick disk forms through continuous processes, such as during a dissipational disk collapse or through secular kinematic diffusion of stars from a thin-disk configuration into a thick one.
Issue Date:1996
Rights Information:Copyright 1996 Bell, David James
Date Available in IDEALS:2011-05-07
Identifier in Online Catalog:AAI9702460
OCLC Identifier:(UMI)AAI9702460

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