2010MNRAS.405..638R

This is the third paper on the morphological analysis of HI features. As in the first paper, we use the mathematical formalism of the metric space technique, developed by F. C. Adams and J. Wiseman, to quantify the complexity of 21-cm interstellar maps. This method compares the one-dimensional `output functions' of the maps, which characterize specific morphological and kinematical aspects of the maps. The HI feature catalogue, from our first paper, is increased from 28 to 51 features of known origin, such as star formation regions, the environment of Wolf-Rayet (WR) stars and supernova remnants. The maps come from the Canadian Galactic Plane Survey (CGPS), and have a resolution of 1 cos δ arcmin. Also, significant improvements are applied to the metric space technique. We present a new data reduction technique, new and improved `output functions' and a better characterization of the noise propagation and uncertainties in functions. We again look for correlations between the complexity of the HI features and other intrinsic aspects such as age, excitation parameter u, wind velocity,|z| and distance. Many interesting correlations are measured, for example: (i) more complex HI is associated with intense flux emission from star formation regions; (ii) the higher the wind velocity of the WR star, the more complex the HI topology; (iii) the higher the HI feature above the Galactic plane, the less complex its topology.