2019/11/26 by Igor I. Zinchenko, Sheng-Yuan Liu, Yu-Nung Su +2
Physics and Astronomy · #astro-ph.GA
paper · pdf · doi:10.3847/1538-4357/ab5c18
15 pages, 14 figures, accepted by the Astrophysical Journal
arxiv created 2019/11/26 · arxiv updated 2020/02/05
We investigate at a high angular resolution the spatial and kinematic structure of the S255IR high mass star-forming region, which demonstrated recently the first disk-mediated accretion burst in the massive young stellar object. The observations were performed with ALMA in Band 7 at an angular resolution ∼ 0.1′′, which corresponds to ∼ 180 AU. The 0.9 mm continuum, C34S(7-6) and CCH N=4-3 data show a presence of very narrow ( ∼ 1000 AU), very dense (n∼ 107 cm-3) and warm filamentary structures in this area. At least some of them represent apparently dense walls around the high velocity molecular outflow with a wide opening angle from the S255IR-SMA1 core, which is associated with the NIRS3 YSO. This wide-angle outflow surrounds a narrow jet. At the ends of the molecular outflow there are shocks, traced in the SiO(8-7) emission. The SiO abundance there is enhanced by at least 3 orders of magnitude. The CO(3-2) and SiO(8-7) data show a collimated and extended high velocity outflow from another dense core in this area, SMA2. The outflow is bent and consists of a chain of knots, which may indicate periodic ejections possibly arising from a binary system consisting of low or intermediate mass protostars. The C34S emission shows evidence of rotation of the parent core. Finally, we detected two new low mass compact cores in this area (designated as SMM1 and SMM2), which may represent prestellar objects.