Infrared Colors as Type Indicators for Spiral Galaxies

Hawarden et al. (1986a, 1986b) present evidence for a segregation between normal spirals and barred spirals in an infrared color-color diagram. They find that remarkably few SA systems have 100 micron/25 micron flux ratios less than about 15 or 25 micron/12 micron colors greater than about 2. Such a segregation could provide a useful means of identifying some edge-on barred spirals. We perform a similar analysis using galaxies chosen from the Second Reference Catalogue of Bright Galaxies (RC2) and find that the results are unexpectedly sensitive to both the selection criteria and the choice of catalog. Although the SA and SB color distributions are different, a given galaxy or group of galaxies cannot be assigned a definite type based on these infrared colors alone.