PREVIOUSLY UNRESOLVED IRAS SOURCES IN THE RHO-OPH A CLOUD

A maximum entropy method (MEM), in which no prior information of struc ture in the field is given to the maximum entropy routines, is used to construct an IRAS image of the central region of the rho Oph A dark c loud in each of the IRAS wavebands (12, 25, 60 and 1 00 pm). Six sourc es are detected in two or more wavebands in the 10 x 12 arcmin 2 area mapped. All six are coincident with near-IR sources known from ground- based observations, although four of the six have not been previously separated in the IRAS data using any other method. The other two sourc es, which are listed in the IRAS Point Source Catalog, were recovered by the MEM in their correct positions. No spurious or unidentified sou rces were generated by the MEM. Two other claimed faint IRAS sources w ithin the field, which are not in the IRAS Point Source Catalog, were not detected by the MEM. The typical gain in resolution of the images reconstructed by the MEM over standard methods is 1.5-2 in the in-scan direction and 3-10 in the cross-scan direction. The mean FWHM of the sources is 0.5 arcmin at 12 and 25 mum, 1 arcmin at 60 mum and 1.5 arc min at 100 mum. The flux densities and luminosities of all six sources are derived, and the flux densities for the two known IRAS sources ag ree within errors with those listed in the Point Source Catalog. The f lux densities of two others are consistent with extrapolations of meas urements made at other wavelengths, and typical errors are estimated t o be approximately 10-30 per cent. 3sigma upper limits are placed on t he IRAS flux densities of the submillimetre sources SM1 and VLA1623, w hich are lower than any previously obtained. The six sources are class ified according to their infrared SEDs.