An infrared and optical study of bright IRAS point sources of minimum apparent temperature

A sample of 170 sources from the IRAS Point Source Catalog (PSC) havingb≥ 40°, 100μm flux F₄ ≥ 2.5 Jy, and upper limit fluxes at 12, 25 and 60μm was studied on POSS and ESO photographic plates. 151 of these sources are identified as 'infrared cirrus,' thirteen as galaxies, and one as a planetary nebula; four sources lie in the Small Magellanic Cloud (SMC), and the remaining source is Saturn. Accurate infrared fluxes were obtained for 29 cirrus sources, the galaxies, and the planetary nebula. The colors of the cirrus sources support the hypothesis that the radiation is coming from a mixture of large, cool grains and Polycyclic Aromatic Hydrocarbons (PAHs), with large variation in relative abundances. Optical colors and surface brightness were obtained for one cirrus cloud using data from the CCD Transit Instrument on Kitt Peak