Project Title: Sizes of Nearby Galaxies
Project Description:
The problem to be addressed is: does the physical diameter of neutral
Hydrogen gas in galaxies scale with galaxy luminosity? If so, what is
the appropriate relation and how does it compare with the stellar
(optical) diameter-luminosity scaling law found by Holmberg (1975).
Evaluation of this result will involve an analytical analysis of
existing data taken from the literature and recent thesis work
measuring the H I sizes of nearby galaxies.
Background Information:
The technique of QSO absorption lines provides a unique tool for
measuring the gaseous properties of galaxies from z=0 up to very high
redshifts -- at distances often too great to discern galaxy properties
directly. Using the observed number density of intervening absorption
lines, one can derive the sizes of gaseous galaxy halos necessary to
produce such lines if one assumes some radius-luminosity scaling law,
and that the local galaxy luminosity function also holds at high
redshifts. The standard practice is to assume the Holmberg relation
holds for gas as well as stars, and then derive halo sizes
accordingly. In this project, we will attempt to evaluate a precise
relationship for dense gas in disk galaxies, we will compare this with
the stellar relation, and we will investigate consequences of the
result as it applies to QSO absorption line studies.
Literature References:
Holmberg, E. 1975, in "Galaxies and the Universe, Volume 9 of Stars
and Stellar Systems", eds. Sandage, Sandage, & Kristian (Univ. of
Chicago Press), Chapter 4 (especially Section 6).
Sargent, W. L. W. 1988, in "Large Scale Structures of the Universe,
Proceedings of IAU Symposium 130", eds. Audouze, Pelletan & Szalay
(Kluwer Publ.), p 333. Also, Bergeron, J. (same volume), p. 343.
Lanzetta, K. M. 1992, PASP, 104, 835.
Steidel, C. C. 1993, in "The Environment and Evolution of Galaxies,
Proceedings of the Third Teton Summer School", eds. Shull & Thronson
(Kluwer Publ.), p. 263.
Requirements:
The sponsor requires that interested students meet the following
requirements: Astronomy or Physics Major, Unix and Programming (C or
Fortran) Experience, Completed two years of coursework including Ay 20
and 21.
This opportunity is for:
Caltech students only
Research Sponsor
Sponsor: Donna S. Womble
Division: PMA
Mail Code: 105-24
Phone: 395-6587
E-mail: dsw@astro.caltech.edu