Infrared mapping of the Galactic plane. IV - The Galactic center

Mid-infrared observations of the galactic center region were obtained at 4, 11, 20, and 27 microns on three rocket-borne experiments. The diffuse emission around the galactic center can be separated into three components: (1) a foreground emission from the galactic disk and the 4-5 kpc ring, (2) a spheroidal component surrounding the center, due to unresolved stellar sources of T greater than 2000 K, and (3) a diffuse elliptical component immediately surrounding the galactic center. The color temperatures of (1) and (3) are consistent with an interpretation of a two-component source of emission from warm dust (about 400 K) characteristic of circumstellar dust shells and cooler dust from extended low-density H II regions. Current models for the infrared emission from interstellar grains cannot reproduce the present spectral distribution in the mid-infrared.