Properties of dense cores in clustered massive star-forming regions at high angular resolution

We aim at characterizing dense cores in the clustered environments associated with intermediate-/high-mass star-forming regions. For this, we present a uniform analysis of Very Large Array NH3 (1,1) and (2,2) observations towards a sample of 15 intermediate-/high-mass star-forming regions, where we identify a total of 73 cores, classify them as protostellar, quiescent starless, or perturbed starless, and derive some physical properties. The average sizes and ammonia column densities of the total sample are similar to 0.06 pc and similar to 10(15) cm(-2), respectively, with no significant differences between the starless and protostellar cores, while the linewidth and rotational temperature of quiescent starless cores are smaller, similar to 1.0 km s(-1) and 16 K, than linewidths and temperatures of protostellar (similar to 1.8 km s(-1) and 21 K), and perturbed starless (similar to 1.4 km s(-1) and 19 K) cores. Such linewidths and temperatures for these quiescent starless cores in the surroundings of intermediate-/high-mass stars are still significantly larger than the typical linewidths and rotational temperatures measured in starless cores of low-mass star-forming regions, implying an important non-thermal component. We confirm at high angular resolutions (spatial scales similar to 0.05 pc) the correlations previously found with single-dish telescopes (spatial scales greater than or similar to 0.1 pc) between the linewidth and the rotational temperature of the cores, as well as between the rotational temperature and the linewidth with respect to the bolometric luminosity. In addition, we find a correlation between the temperature of each core and the incident flux from the most massive star in the cluster, suggesting that the large temperatures measured in the starless cores of our sample could be due to heating from the nearby massive star. A simple virial equilibrium analysis seems to suggest a scenario of a self-similar, self-gravitating, turbulent, virialized hierarchy of structures from clumps (similar to 0.1-10 pc) to cores (similar to 0.05 pc). A closer inspection of the dynamical state taking into account external pressure effects reveals that relatively strong magnetic field support may be needed to stabilize the cores, or that they are unstable and thus on the verge of collapse.