Astronomy and Astrophysics – Astronomy
Scientific paper
Apr 1993
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1993pasp..105..442e&link_type=abstract
Publications of the Astronomical Society of the Pacific, v.105, p.442
Astronomy and Astrophysics
Astronomy
Scientific paper
The global properties of galaxies such as their observed luminosities may be severely affected by internal obscuration of the stars by dust. In this thesis I examine the amount and extent of this obscuration using the following approaches: For a sample of eight galaxies for which I have obtained multi-waveband optical and near-infrared observations I have investigated the reddening of individual regions, the optical depth inferred from hydrogen column densities (using an assumed gas to dust ratio) and the optical depth calculated using a detailed energy balance between the observed stellar and far infrared (FIR) fluxes. In addition I investigate the variation of the scale length of galaxies at different wavelengths and the variation of galaxies' blue magnitudes with inclination. I find that two of these tests which are sensitive to zeta, the relative vertical scale heights of the stars and dust, suggest that values of zeta >/= 0.5 are necessary to be consistent with the data. The observed B-band central optical depths of my sample are found to vary between ~2 and ~25. I suggest a value of ~8 +/- 3 fora `typical' spiral galaxy. Such a galaxy would be optically thick to beyond its half-light radius, and it would have an extinction of 0.75 mag (50% of the blue luminosity). However, uncertainties still remain as many of my conclusions are based on a small data set. More observations of a larger sample, together with observations beyond 100 microns, are required to solve this important problem. (SECTION: Dissertation Abstracts)
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