University of Illinois Urbana-Champaign

A Kinematic and Abundance Survey of the Galactic Pole Regions

Hartkopf, William Irving

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Description

Title
A Kinematic and Abundance Survey of the Galactic Pole Regions
Author(s)
Hartkopf, William Irving
Issue Date
1981
Department of Study
Astronomy
Discipline
Astronomy
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Physics, Astronomy and Astrophysics
Language
eng
Abstract
  • DDO observations of 1076 G and K stars at the north and south galactic poles are combined with published photometry to give a new abundance gradient perpendicular to the galactic plane to z-distances greater than 5 kpc. Additional DDO photometry of bright field stars has been used to calibrate the DDO abundance index against {Fe/H} for metal-poor stars.
  • The resulting gradient in {Fe/H} is about -0.33 kpc('-1) out to 2 kpc, decreasing to about -0.23 kpc('-1) for 2 < z < 5 kpc. The discrepancy between earlier results (utilizing only the DDO CN anomaly) and the present values is resolved. The distribution in metallicity found for K-giants above 1 kpc is consistent with Searle and Zinn's (1978 Astrophys. J. 225,357) idea that the halo formed by the merging of a number of star-forming regions or "fragments". Gas lost from these fragments condensed into the plane and provided material for enrichment of the disk.
  • Radial velocities observed for 302 for our polar giants, coupled with published velocities, have enabled us to determine the z-component of the velocity dispersion to a height of over 4 kpc. In combination with the photometry, the radial velocities allow us to determine velocity dispersions as a function of abundance, as well. The abundances found for our high-z stars is similar to the A-star results of Rodgers (1971 Astrophys. J. 244,912), in that about half of the K-giants above 1 kpc have solar abundances. The kinematic differences between Rodgers' stars and ours are inconsistent with the idea of a common origin, however.
  • Finally, we also calculate new values of the perpendicular acceleration function K(,z)(z) at high z-distances and investigate the sensitivity of K(,z) determinations to the density function used. The need for a new, more extensive D(z) determination is discussed.
Graduation Semester
1981
Type of Resource
text
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http://hdl.handle.net/2142/67510

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