The Spatial–Kinematic Structure of the Region of Massive Star Formation S255N on Various Scales

Abstract

The results of a detailed analysis of SMA, VLA, and IRAM observations of the region of massive star formation S255N in CO(2–1), N₂H⁺(3–2), NH₃(1, 1), C¹⁸O(2–1) and some other lines is presented. Combining interferometer and single-dish data has enabled a more detailed investigation of the gas kinematics in the moleclar core on various spatial scales. There are no signs of rotation or isotropic compression on the scale of the region as whole. The largest fragments of gas (≈0.3 pc) are located near the boundary of the regions of ionized hydrogen S255 and S257. Some smaller-scale fragments are associated with protostellar clumps. The kinetic temperatures of these fragments lie in the range 10–80 K. A circumstellar torus with inner radius R_in ≈ 8000 AU and outer radius R_out ≈ 12 000 AU has been detected around the clump SMA1. The rotation profile indicates the existence of a central object with mass ≈8.5/ sin²(i) M_⊙. SMA1 is resolved into two clumps, SMA1–NE and SMA1–SE, whose temperatures are≈150Kand≈25 K, respectively. To all appearances, the torus is involved in the accretion of surrounding gas onto the two protostellar clumps.