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We have mapped at small spatial scales the temperature and the velocity fieldin the protocluster associated with IRAS 05345+3157, which contains bothintermediate-/high-mass protostellar candidates and starless condensations, andis thus an excellent location to investigate the role of massive protostars onprotocluster evolution. We observed the ammonia (1,1) and (2,2) inversiontransitions with the VLA. Ammonia is the best thermometer for dense and coldgas, and the observed transitions have critical densities able to trace thekinematics of the intracluster gaseous medium. The ammonia emission is extendedand distributed in two filamentary structures. The starless condensations arecolder than the star-forming cores, but the gas temperature across the wholeprotocluster is higher (by a factor of ~1.3-1.5) than that measured typicallyin both infrared dark clouds and low-mass protoclusters. The non-thermalcontribution to the observed line broadening is at least a factor of 2 largerthan the expected thermal broadening even in starless condensations, contraryto the close-to-thermal line widths measured in low-mass quiescent dense cores.The NH3-to-N2H+ abundance ratio is greatly enhanced (a factor of 10) in thepre--stellar core candidates, probably due to freeze-out of most molecularspecies heavier than He. The more massive and evolved objects likely play adominant role in the physical properties and kinematics of the protocluster.The high level of turbulence and the fact that the measured core masses arelarger than the expected thermal Jeans masses indicate that turbulence likelywas an important factor in the initial fragmentation of the parental clump.

Temperature and kinematics of protoclusters with intermediate and high-mass stars: the case of IRAS 05345+3157