NEW OH IR STARS FROM COLOR-SELECTED IRAS SOURCES .3. A COMPLETE SURVEY

We present the results of 1612 MHz observations conducted at the Areci bo Observatory of 571 color-selected sources from the IRAS Point Sourc e Catalog. Of these sources we detect 132, 113 for the first time. Thi s is the third part of an Arecibo survey of color-selected IRAS source s. The earlier two parts together detected a total of 268 sources of 1 612 MHz emission. An analysis of the properties of the OH/IR stars det ected in all three parts of the survey is included. In particular we c ompute the limiting 1612 MHz peak flux of the entire survey to be appr oximately 40 mJy. The correlation between the IRAS infrared fluxes and the 1612 MHz flux of the 132 sources detected in part III of the surv ey is smaller than that found in the earlier parts of the survey. This is to be expected from the intrinsic variability of OH/IR stars and t he longer time gap between the 1612 MHz observations and the IRAS meas urements. We identify a subset of 54 stars as being near the tangent p oint of the galactic rotation curve. Using the kinematical distances t o these stars we find that the efficiency of momentum transfer varies exponentially with the (25 - 12) mum color, consistent with the stella r outflow being driven by radiation pressure. Further the IR pump effi ciency increases with increasing optical depth of the circumstellar sh ell, as expected for radiative pumping. The bolometric luminosity func tion is found to decrease sharply above L(Bol) = 5600 L., and the 1612 MHz luminosity function shows a corresponding falloff above L1612 = 1 .8 x 10(-8) L.. We also find direct confirmation of the expectation th at sources with large expansion velocity are more luminous than source s with small expansion velocity.