HIGH SPATIAL-RESOLUTION MAPPING OF THE CEPHEUS A REGION AT 20-MICRON, 50-MICRON, AND 100-MICRON

We have mapped a 50″ x 30″ region in Cepheus A with a 4″ beam at 20 μm. We observed a bright, unresolved, central source with peak flux of 41 Jy into our beam, but otherwise detected no 20 μm emission in the region down to a 3 σ upper limit of 3 Jy per pixel. We also obtained one-dimensional scans across Cepheus A at 50 and 100 μm using diffraction limited slit apertures. In all the scans the source is noticeably resolved in comparison to the point source profiles. From these data we calculate spatial profiles of the 50/100 μm color temperature and 100 μm optical depth. The temperature profile is relatively flat, with a maximum value of 46 K, while the optical depth shows a well-defined peak in the dust column density with a maximum 100 μm optical depth of 0.4. Within errors, the position of the peak of the far-infrared emission is found to be the same as the 20 μm source. Application of a maximum entropy deconvolution technique to the 50 μm and 100 μm profiles yields spatial resolution better than the diffraction limit. It is apparent from these deconvolutions that the far-infrared source consists of a bright, compact core with clumpy extended emission. We have constructed models of the far-infrared source and generated theoretical slit scans to compare with our observations. These calculations demonstrate that the 100 μm optical depth through the center of the Cepheus A cloud could be a factor of 2 or more higher than the value (0.4) we have derived from a simple slab model. We interpret these data to indicate that a deeply embedded object with L ≈ 2.5 x 104 L⊙ is the main luminosity source in the Cepheus A region.