Kinematic and Abundance Gradients in the Galactic Disk

Radial velocities and DDO and BV photometry of 364 G and K stars in the galactic center and anticenter directions have been obtained for the purpose of investigating the gradients of abundance and velocity dispersion in the galactic disk. The abundance gradient found for these stars is d (Fe/H) /dR = $-$0.017 $\pm$.007 dex/kpc, which is similar to the gradients found in other studies of mixed-age objects. $U$ velocity dispersion is found to depend on both metal abundance and galactocentric distance. For stars observed in the galactic center direction, the highest velocity dispersion is found in the metal-rich stars, a result which is suggestive of the existence of an old metal-rich population in the inner disk. For the stars observed in the anticenter direction, the dependence is more in accord with the conventional picture of increasing velocity dispersion with time and increasing metal abundance with age. Here, the metal-poor stars are found to have higher velocity dispersion than the normal-abundance stars. The gradient in $U$ velocity dispersion with galactocentric distance is found to be dσ\sb{U}/dR = $-$3.8 $\pm$ 0.6 km/sec/kpc over a distance range of 14 kpc. This result implies that the relationship between velocity dispersion and age which is observed for stars in the neighborhood of the sun cannot apply unchanged to stars in other parts of the disk. Simple calculations of the effect of the observed distribution of molecular clouds on the kinematics in the disk suggest that this mechanism could produce the observed velocity dispersion gradient. To test this suggestion observationally, a program to measure the variation of the kinematic-age relationship with galactocentric distance is suggested.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Astronomy

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2014

Author dc:creator

• Neese, Carol Lynn

Contributors dc:contributor

• Yoss, Kenneth M.

• Physics, Astronomy and Astrophysics

Identifier

(UMI)AAI8803151

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/70668