IRAS SOURCES BEYOND THE SOLAR CIRCLE .6. ANALYSIS OF THE FIR, H2O, AND CO EMISSION

For a sample of 1357 IRAS sources with FIR colours of young stellar ob jects we have compared the occurrence and properties of H2O maser- and (CO)-C-12(1-0) emission with the observed and derived IRAS parameters . We find that the distribution of differences between the CO and H2O velocities is a Gaussian with a FWHM of about 11 km s(-1). The mean ve locity difference is nearly zero. The velocity of the peak H2O emissio n is not at a preferred location within the velocity interval where em ission is detected. The H2O maser detection rate increases with both t he FIR luminosity and the (CO)-C-12(1-0) line width: below log(L(FIR)/ L.)=3.5, less than 10% of the sources show maser emission, whereas H2O is detected towards almost all of the sources above log(L(FIR)/L.)=4. 5. For the sources with H2O maser emission, the average CO line width (FWHM about 5.0 km s(-1)) is approximately twice as large as for those without detected H2O emission, an effect which is independent of the sources' FIR luminosity. However a significant fraction of sources wit h no detected H2O emission still have line widths larger than 1.9 km s (-1), the median value for the quiescent gas not associated with the I RAS sources. The maximum H2O maser luminosity at each FIR luminosity i s proportional to L(FIR): L(H2O)/L.=10(-7.4)(L(FIR)/L.). In IRAS colou r-colour plots, sources can be distinguished in maser-like and non-mas er-like sources according to their CO line widths and FIR luminosity. At a given L(FIR) the maximum T-A() found for (1CO)-C-2(1-0) decrease s with distance from the Sun, likely due to beam filling effects. Few sources with maser emission have T-A() below 7.5 K, when observed wit h the IRAM 30-m telescope. There is no difference in the maximum T-A( ) of sources with maser-like and non-maser-like IRAS colours. We have derived the intrinsic luminosity- and mass distribution of sources wit h (non)-maser-like IRAS colours, correcting for incompleteness effects at lower luminosities. The slope of the IMF for sources with maser-li ke colours and mass larger than 10 M. is found to be -2.8 +/- 0.3.