High Spatial Resolution CN and CS Observation of Two Regions of Massive Star Formation

Molecular line CN, CS and mm continuum observations of two intermediate- tohigh-mass star-forming regions - IRAS20293+3952 and IRAS19410+2336 - obtainedwith the Plateau de Bure Interferometer at high spatial resolution revealinteresting characteristics of the gas and dust emission. In spite of theexpectation that the CN and CS morphology might closely follow the dense gastraced by the dust continuum, both molecules avoid the most central cores.Comparing the relative line strengths of various CN hyperfine components, thisappears not to be an opacity effect but to be due to chemical and physicaleffects. The CN data also indicate enhanced emission toward the differentmolecular outflows in the region. Regarding CS, avoiding the central cores canbe due to high optical depth, but the data also show that the CS emission isnearly always associated with the outflows of the region. Therefore, neither CSnor CN appear well suited for dense gas and disk studies in these two sources,and we recommend the use of different molecules for future massive diskstudies. An analysis of the 1 and 3mm continuum fluxes toward IRAS20293+3952reveals that the dust opacity index beta is lower than the canonical value of2. Tentatively, we identify a decreasing gradient of beta from the edge of thecore to the core center. This could be due to increasing optical depth towardthe core center and/or grain growth within the densest cores and potentialcentral disks. We detect 3mm continuum emission toward the collimated outflowemanating from IRAS20293+3952. The spectral index of alpha ~ 0.8 in this regionis consistent with standard models for collimated ionized winds.Comment: 5 pages, 2 tables, 9 figures, accepted for Ap