Infrared surface brightness distributions of galaxies.

Near-infrared (1.2-2.2 micron) surface brightness measurements across the faces of a sample of nearby galaxies are presented, employing a variety of instrumental techniques. NGC 2683, 4565, and 5907 are seen almost edge-on, and for two of these, optical (V) data were obtained simultaneously with the infrared, using a widethrow-chop two channel photometer developed at Leicester by Dr.D.J.Adams. The results of these observations are presented in a single Chapter (3), in which the infrared measurements are used to define obscuration-free scale sizes for the disks, and the optical- infrared colours place constraints on possible mechanisms for the production of colour-index gradients. The remaining observational chapters (2 & 4) are a chronological record of use of the infrared system of the Anglo-Australian Telescope, documenting steps toward DC-mapping of extended objects, begun in 1980 with semi-DC observations of NGC 5128 at 2.2 microns (Chapter 2). Significant data were obtained in the course of these experiments, and in the final chapter we present J, H and K maps of M83, a large face-on spiral, which were obtained with the intention both of resolving the controversy over the Freeman Type I- Type II surface brightness profiles, and of detecting the density wave in the "old disk", suspected to drive the optical spiral star formation pattern. Our discussion of these observations also contains a number of warnings about the pitfalls which lurk in the DC-measurement process, most of which are concerned with the knowledge (or lack of it) of the sky background level when observing very extended objects. The first chapter gives a short introduction to some of the outstanding problems of extragalactic astronomy, and the uses to which infrared measurements can be put in tackling these problems. The overall objective of the Thesis is to illustrate, through observational results, the wide range of applications which near- infrared imaging finds in studies of galaxies. The contrast between the three observational chapters highlights this point.