文章基本信息

标题：A multi-molecular line study of the star-forming globule CB88-230
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作者：J. Brand ; J. G. A. Wouterloot ; C. Codella 等
期刊名称：Astronomy & Astrophysics
印刷版ISSN：0004-6361
电子版ISSN：1432-0746
出版年度：2019
卷号：628
页码：1-15
DOI：10.1051/0004-6361/201935731
语种：English
出版社：EDP Sciences
摘要：Context.This paper relates to low-mass star formation in globules, and the interaction of newly-formed stars with their environment. We follow up on the results of our earlier observations of this globule.Aims.Our aim is to study the gas- and dust environment of the young stellar object (YSO) in globule CB88 230, the large-scale molecular outflow triggered by the jet driven by the YSO, and their interaction.Methods.We carried out submillimetre continuum and multi-line molecular observations with several single-dish facilities, mapping the core of the globule and the large-scale outflow associated with the YSO.Results.Dust continuum and molecular line maps (of12CO, C18O, CS, CH3OH) show a flattened (axes ratio 1.5−1.7), asymmetric core with a full width at half maximum (FWHM)-diameter of 0.16−0.21 pc. Line profiles of12CO,13CO(2–1, 3–2), and CS(2–1) show self-absorption near the YSO; the absorption dip is at a slightly (~0.3 km s−1) redder velocity than that of the quiescent gas, possibly indicating infall of cooler envelope gas. The mass of the core, determined from C18O(1–0) observations, is about 8M⊙, while the virial mass is in the range 5−8M⊙, depending on the assumed density distribution. We detect a slight velocity gradient (~0.98 km s−1pc−1), though rotational energy is negligible with respect to gravitational and turbulent energy of the core. A fit to the spectral energy distribution of the core gives a dust temperatureTd≈ 18 K and a gas mass of ca. 2M⊙(assuming a gas-to-dust ratio of 100). More careful modelling of the sub-mm emission (not dominated by the relatively hot central regions) yieldsM≈ 8M⊙. From the molecular line observations we derive gas temperatures of 10−20 K. A Bayesian analysis of the emission of selected molecules observed towards the YSO, yieldsTkin≈ 21.4 K (68% credibility interval 14.5−35.5 K) and volume densityn(H2) ≈ 4.6 × 105cm−3(8.3 × 104−9.1 × 105cm−3). We have mapped the well-collimated large-scale outflow in12CO(3–2). The outflow has a dynamical age of a few 104yr, and contains little mass (a few 10−2M⊙). A misalignment between the axis of this large-scale outflow and that of the hot jet close to the YSO indicates that the outflow direction may be changing with time.
关键词：Key wordsenstars: formationstars: pre-main sequenceISM: cloudsISM: jets and outflowsISM: individual objects: CB88-230