THE SUBARCSECOND INFRARED STRUCTURES AT THE CENTERS OF INFRARED-LUMINOUS GALAXIES

We present 1.6-2.2 μm imaging observations of the centers of nine galaxies with high 60-100 μm luminosities. Eight of the nine galaxies contain central 2.2 μm sources that are larger than the point spread function, which typically had a size (FWHM) of 1″.0. The typical physical size of the 2.2 μm sources is ≃0.5 kpc. One of the galaxies (NGC 6240) contains a double source, with the components having a similar separation (≃1″.5) and position angle to the radio and optical components. The central (≃0.5 kpc) regions of six out of the nine galaxies have 2.2 μm surface brightnesses that are equal to or greater than the maximum 2.2 μm central surface brightness of a sample of optically selected galaxies. The H-K colors of the central regions of the infrared-luminous galaxies are ∼0.5 mag redder than the colors of the central regions of optically selected galaxies. The result that the nuclear 2.2 μm sources in almost all of the galaxies are extended is evidence that most of the 2.2 μm emission is from sources other than active nuclei.