Spatial distributions and kinematics of shocked and ionized gas in M17

Abstract

Massive stars are formed in molecular clouds, and produce H II regions when they evolve onto the main sequence. The expansion of H II region can both suppress and promote star formation in the vicinity. M17 H II region is a giant cometary H II region near many massive clumps containing starless and protostellar sources. It is an appropriate target to study the effect of feedback from previously formed massive stars on the nearby star-forming environments. Observations of SiO 2-1, HCO${}^{+}$ 1-0, H${}^{13}$CO${}^{+}$ 1-0, HC${}_3$N 10-9, and H41$\alpha$ lines are performed toward M17 H II region with ambient candidates of massive clumps. In the observations, the widespread shocked gas surrounding M17 H II region is detected: it probably originates from the collision between the expanding ionized gas and the ambient neutral medium. Some massive clumps are found in the overlap region of the shock and dense-gas tracing lines while the central velocities of shocked and high-density gases are similar. This suggests that part of massive clumps are located in the shell of H II region, and may be formed from the accumulated neutral materials in the shell. In addition, by comparing the observations toward M17 H II region with the simulation of cometary H II region, we infer the presence of one or more massive stars travelling at supersonic velocity with respect to the natal molecular cloud in the H II region.

13 pages, 11 figures

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Cited by in corpus (3)

• ATOMS: ALMA Three-millimeter Observations of Massive Star-forming regions -- XIX. The origin of SiO emission
• Origins of the shocks in high-mass starless clump candidates
• An nl-model with a full radiative transfer treatment for level populations of hydrogen atoms in a spherically symmetric H II region