An infrared survey of the diffuse emission within 5 ̊of the galactic plane

About this book

The AFGL Infrared Sky Survey data have been processed to deconvolve the low frequency attenuation, restoring the signals from extended sources. The 11 and 20-micrometer scans which cover three quarters of the galactic plane have been analyzed, with lesser area covered at 4 and 27 micrometers. A detailed description is given of the instrumentation, the conduct of the experiment, and the data reduction procedures. The measured extended emission in the 3- to 30-micrometer region may be divided into several components. A number of discrete, extended sources are observed within 5 deg of the galactic plane, the majority of which are associated with HII regions. About 25 percent of these sources are not in the AFGL catalog. A large scale diffuse emission is centered on the galactic plane at longitudes less than 90 deg from the galactic center. The 11 to 20-micrometer color ratio of this emission is distinctly smaller in the direction of the Perseus external arm and the Sagittarius-Carina spiral than closer to the center (1 <65 deg). Most of this background is probably due to thermal radiation from HII regions along the line of sight. Interior to approx. 65 deg, the 4-micrometer measurements can be understood in terms of the 2.4-micrometer balloon-borne survey observation and interpreting the background at both wavelengths as being due to late type stars. The 20-micrometer values over these longitudes are probably due to HII regions. Additional 11-micrometer sources are required to explain the measured values.