Morphological parameters of galaxies from Spitzer

We explore where normal, non-interacting galaxies--those typically found on the Hubble tuning fork--lie in this parameter space and show that there is a tight relation between concentration (C_82_) and M_20_ for normal galaxies. M_20_ can be used to classify galaxies into earlier and later types (i.e., to separate spirals from irregulars). Several criteria using these parameters exist to select systems with a disturbed morphology, i.e., those that appear to be undergoing a tidal interaction.

We examine the applicability of these criteria to Spitzer NIR imaging. We find that four relations, based on the parameters A and S, G and M_20_, G_M_, C, and M_20_, respectively, select outliers in morphological parameter space, but each selects different subsets of galaxies. Two criteria (G_M_>0.6,G>-0.115xM_20_+0.384) seem most appropriate to identify possible mergers and the merger fraction in NIR surveys.

We find no strong relation between lopsidedness and most of these morphological parameters, except for a weak dependence of lopsidedness on concentration and M_20_.