The development of CCD image processing techniques and their application to surface photometry of NGC 6166

Abstract

A systematic procedure for processing and reducing CCD-generated images has been developed. It involves removing unwanted objects and blemishes, subtracting the bias offset, removing the thermal background; correcting for areal sensitivity variations, and removing the sky background. This procedure has been applied to images of the cD galaxy NGC 6166 in Abell cluster 2199. Surface brightness profiles in B and R and a (B-R) colour profile have been generated for NGC 6166. Between 15 and 45 kpc the surface brightness profiles agree with the data of Oemler (1976), but beyond 45 kpc our profiles decline rapidly. The (B-R) colour profile shows that the galaxy becomes bluer by 0.03 mag between galactocentric distances of 15 and 33 kpc in agreement with pervious observations. These results are tentative, pending improvement of our method of determining the sky background and examination of the complete set of data.