IR photometric data at wavelengths from 1.6 through 34 microns are reported for the nucleus of NGC 253. Maps and image-tube photographs of the nucleus are presented, and they indicate that most of the 10-micron flux comes from a region about 45 pc in diameter, the 2.2-micron flux is more extended, and the 10-micron core is at the position of a compact radio source. The silicate absorption feature at 10 microns is found to vary in strength across the source, indicating strong nonuniform interstellar extinction, and the ratio of its optical depth to the visual extinction is similar to that found toward our galactic center. The M/L ratio in the nucleus is determined to be less than 0.1, and it is concluded that thermonuclear burning of the current nucleus mass could not have sustained the present emission level for the life of the galaxy.
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Rieke et al. (1975) studied this question.