NEAR-INFRARED IMAGING OF INTERACTING GALAXIES

A sample of 22 interacting galaxies has been imaged in the J (1.25 μm) and K (2.2 μm) bands using an array camera providing a resolution of 0″.76 pixel-1. The majority of observed systems are disk-type galaxies. These images have been compared with optical R and Hα images in order to determine the degree of correlation between the optical and near-infrared morphologies of the galaxies. In most cases the large-scale near-infrared structure is similar to that seen in optical continuum images. However, in many systems there are small-scale morphological features that are strikingly different from their optical counterparts, which we believe to be due mainly to the obscuring effect of dust at optical wavelengths. In some galaxies the near-infrared images have revealed the locations of previously invisible nuclei. In general, there is little correlation between the near-infrared and Hα morphologies of the galaxies. Only the very brightest H II complexes stand out from the background stellar population in the infrared images. The nuclei of most of the observed galaxies are redder than their disk regions. The ratio of color changes in R - K and J - K is less than the value for reddening by dust alone, suggesting that metallicity and population gradients are also present. It appears that little, if any, of the red nuclear colors is due to thermal emission from dust. Magnitudes and colors measured from the near-infrared images are in excellent agreement with photometry obtained using single-channel detectors.