High – resolution imaging of NH 3 inversion lines toward W 3 main

Three-arcsecond angular resolution (0.03 pc at 2.3 kpc) images of the (J,K) = (1,1) and (2,2) NH3 inversion lines toward W3 Main are presented. These observations show NH3 emission from individual clumps and filaments embedded in the lower density ammonia gas, previously observed with a spatial resolution of 40′′. Toward the molecular core W3 East we detect NH3 emission with broad line profiles from a very compact (FWHM ≈ 5′′) and dense clump toward IRS 5 and weaker emission from compact clumps near IRS 11. The molecular clump toward IRS 5 is associated with a cluster of young low–mass stars and hypercompact H ii regions tracing recent high–mass star formation. Toward the molecular core W3 West, which is luminous in the submillimetre but has no embedded H ii continuum or NIR sources, we detect NH3 emission with narrow line profiles from a more extended (≈ 25′′) and clumpy region. A thin NH3 filament, less than 8′′ wide, stretches more than 40′′ away from IRS 4, northeast of W3 West, curving around the compact H ii region W3 H. Toward the ultracompact H ii region W3 B we find ammonia in absorption. The VLA data presented here are in support of models which suggest that star formation seems to be occurring in bursts toward the W3 GMC. Extended NH3 emission is detected only toward a quiescent core with no associated star formation. In comparison, toward the active star–forming cores the NH3 is dispersed and underabundant.