A subdued interpretation of the visual and infrared emission from merging galaxies - Application to NGC 6240

U, R, J, H, and K images of the merging galaxy pair NGC 6240 are presented and interpreted. It is argued that an ultraluminous super-starburst is neither the most obvious nor the sole explanation for many of the observations of this system. In particular, absorption of the light from an older stellar population by a disrupted dusty ISM can contribute a large fraction of the observed emission at long wavelengths. This source of dust heating is estimated to make up between one-fifth and one-half of the total IR luminosity of this galaxy. Model galaxies are also adapted to derive a series of conversions from monochromatic magnitudes to stellar bolometric luminosities. It is also found that the older stellar population contributes an important fraction to the total IR luminosity of other ultraluminous starburst galaxies. 76 refs