Dense Cores, Filaments and Outflows in the S255IR Region of High Mass Star Formation

TL;DR

This study uses high-resolution ALMA observations to analyze the complex structures, outflows, and potential protostellar objects in the high-mass star-forming region S255IR, revealing detailed filamentary, outflow, and core characteristics.

Contribution

It provides the first detailed high-resolution imaging of the S255IR region, uncovering filamentary structures, outflow dynamics, and new prestellar core candidates with unprecedented detail.

Findings

Identification of dense, warm filamentary structures around the core.

Detection of wide-angle outflows and collimated jets with shock signatures.

Discovery of two new low-mass prestellar core candidates.

Abstract

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 $ \sim 0.1^{\prime\prime}$, which corresponds to $ \sim 180 $ AU. The 0.9 mm continuum, C$^{34}$S(7-6) and CCH $N=4-3$ data show a presence of very narrow ($ \sim 1000 $ AU), very dense ($n\sim 10^7$ 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 C$^{34}$S 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.