Dense cloud cores

Abstract

In order to search for ultra-dense gas condensations as possible sites of future star formation, observations with highest possible angular resolution in high-gas density probing molecular species are required. Here we report first results from two-telescope (IRAM 30-m & CSO 10.4-m) multi-transition excitation studies of the linear molecules CS and HCN, both with critical densities ncτ107 cm⁻³. We obtained maps towards a number of galactic cloud cores in the CS(J=5−4;7−6) and the HCN(3−2;4−3) mm/submm transitions and those of their optically thin isotopic species (C³⁴S; H¹³CN) accessible from ground. For a proper excitation analysis, the gas temperature has been determined independently from the symmetric top molecules NH₃ or CH₃CN. Here we present first results obtained towards the NGC 2024 molecular cloud core (Schulz et al. 1990).