A SURVEY FOR DENSE CORES AND YOUNG STELLAR CLUSTERS IN THE W-3 GIANT MOLECULAR CLOUD

We simultaneously mapped the metastable (J,K) = (1,1) and (2,2) invers ion lines of NH3 toward W 3 Main, W 3(OH), and the region between thes e two star-forming clouds with a 40 '' angular resolution using the 10 0-m Effelsberg telescope. We observed a 120 square-arcminute region wi th 20 '' spacing and a significantly higher sensitivity than previous maps. We also measured the (J,K) = (3,3) line of NH3 in 28 positions t oward W 3 Main. For comparison with our NH3 survey, we present a K'-ba nd (2.1 mu m) survey conducted by J. T. Rayner. The K'-band survey det ects five distinct stellar clusters within the mapped region. In addit ion, we compare the NH3 survey to the CO (1-0) maps of the FCRAO 2nd q uadrant survey (Heyer et al. 1998) and to the distribution of H II reg ions. The goals of this new survey are to a) map the extent of dense g as in the W 3 Main and W 3(OH) molecular clouds, b) search for previou sly undetected molecular cores in the intervening molecular cloud, c) measure column densities and T-kin for regions of strong NH3 emission, d) compare the distribution of the NH3 emission to that of the CO emi ssion and e) study the relationship between the ammonia gas and sites of star formation as traced by stellar clusters and H II regions. In t he W 3 Main cloud, we find strong and extended NH3 emission toward the relatively quiescent western core, but only weak and non-extended emi ssion toward the highly active, star-forming, eastern core. We argue t hat the NH3 relative abundance in the eastern core is an order of magn itude lower than that in the western core. Southeast of W 3 Main we de tect a new NH3 core, which we denote W 3 SE. From our NIR images we de tect a jet toward this core. Toward the W 3(OH) cloud, we find an exte nded (2 x 1.3 pc), cold ammonia gas component. We show that the narrow plume of NH3(1,1), detected toward W 3(OH) in VLA maps, is part of a larger NH3 structure extending toward a chain of stellar clusters and nebulosities found in our NIR images. We find that the strong NH3 emis sion detected in the three cores covers 9% of the surveyed region. We estimate virial masses for each NH3 core and find that the total sum o f the virial masses is 3300 MO. The total mass measured from the CO em ission surveyed in this region is 1.6 x 10(4) Mo, thus 20% of the mole cular gas in the surveyed region is found in the dense cores. This ind icates that the dense cores fill only a small fraction of the total GM C and are concentrated in regions of active star formation. We also fi nd extensive weak NH3 emission which covers one fourth of the surveyed region. This weak emission may trace gas with densities just sufficie nt to excite the NH3 emission (10(4) cm(-3)) as well as strongly beam- diluted knots and filaments. We compare in detail the distribution of NH3 cores, young stellar clusters, and H II regions, and discuss the e ffects of star formation on the NH3 cores. We also compare the results of our survey to those discussed by Lada (1992) from the CS (2-1) and 2.2 mu m surveys obtained for the Orion B giant molecular cloud by La da et al. (1991a,1991b).