Galactic noise and the distance to Centaurus A
Shopbell, Patrick Lynn
Master of Science thesis
Deep B and R band photographic plates of the giant radio elliptical NGC 5128 (Centaurus A), obtained under photometric conditions at the f/3.3 prime focus of the AAT 3.9m telescope, clearly show surface brightness fluctuations from the luminous, stellar population. The variance of such fluctuations has been used by Tonry and collaborators to determine distances to nearby galaxies from CCD imagery. This thesis exploits the distinct statistical properties of photographic plates to perform a similar analysis employing this inherently nonlinear detector. The effects of threshold and saturation are discussed in detail. The final derived power spectra can be understood in terms of the noise components previously identified plus an additional component arising from fluctuations in the grain density. The analysis derives a distance to Centaurus A of 3.8 $\pm$ 1.1 Mpc, in close agreement with recent determinations. As a statistically independent test, this work provides strong support for the fluctuation distance method.