1998A&A...336..991T

We simultaneously mapped the metastable (J,K)=(1,1) and (2,2) inversion lines of NH₃ toward W 3 Main, W 3(OH), and the region between these two star-forming clouds with a 40" angular resolution using the 100-m Effelsberg telescope. We observed a 120 square-arcminute region with 20" spacing and a significantly higher sensitivity than previous maps. We also measured the (J,K)=(3,3) line of NH₃ in 28 positions toward W 3 Main. For comparison with our NH₃ survey, we present a K'-band (2.1µm) survey conducted by J. T. Rayner. The K'-band survey detects five distinct stellar clusters within the mapped region. In addition, we compare the NH₃ survey to the CO (1-0) maps of the FCRAO 2nd quadrant survey (Heyer et al., 1998ApJS..115..241H) and to the distribution of H II regions. The goals of this new survey are to a) map the extent of dense gas in the W 3 Main and W 3(OH) molecular clouds, b) search for previously 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 emission and e) study the relationship between the ammonia gas and sites of star formation as traced by stellar clusters and H II regions. In the W 3 Main cloud, we find strong and extended NH₃ emission toward the relatively quiescent western core, but only weak and non-extended emission toward the highly active, star-forming, eastern core. We argue that the NH₃ relative abundance in the eastern core is an order of magnitude lower than that in the western core. Southeast of W 3 Main we detect a new NH₃ core, which we denote W 3 SE. From our NIR images we detect a jet toward this core. Toward the W 3(OH) cloud, we find an extended (2x1.3pc), 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 emission 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 of the virial masses is 3300M☉. The total mass measured from the CO emission surveyed in this region is 1.6x10⁴M_☉, thus 20% of the molecular gas in the surveyed region is found in the dense cores. This indicates that the dense cores fill only a small fraction of the total GMC and are concentrated in regions of active star formation. We also find extensive weak NH₃ emission which covers one fourth of the surveyed region. This weak emission may trace gas with densities just sufficient to excite the NH₃ emission (10⁴cm^–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 effects of star formation on the NH₃ cores. We also compare the results of our survey to those discussed by Lada (1992ApJ...393L..25L) from the CS (2-1) and 2.2µm surveys obtained for the Orion B giant molecular cloud by Lada et al. (1991ApJ...368..432L, 1991ApJ...371..171L).