The position angles determined from galmag are in the range -. They do not go all the way to , since the major axis of a galaxy does not have a positive and a negative direction, as opposed to for example a coordinate axis.
If a galaxy has an isophote twist, i.e. the position angle changes with the radius r, the position angle might cross the upper or lower limit of or , respectively, and thereby appearing discontinuous. This is in a way a cosmetical problem. Since the position angle is only determined to within a factor of , we can add or subtract at certain radii to make the profile look continuous. This was done using the task pa1shift. An example of this is shown in Figure .
Properties of E and S0 Galaxies in the Clusters HydraI and Coma
Master's Thesis, University of Copenhagen, July 1997
Bo Milvang-Jensen (firstname.lastname@example.org)