Two-Dimensional Molecular Gas and ongoing star formation around H II region Sh2-104

TL;DR

This study investigates the molecular gas structure and ongoing star formation around H II region Sh2-104, revealing a double-ring morphology, clump properties, and evidence of collect-and-collapse star formation driven by feedback from massive stars.

Contribution

The paper provides new multiwavelength observations of Sh2-104, demonstrating a two-dimensional ring structure and confirming the collect-and-collapse star formation process in this region.

Findings

Outer ring is a two-dimensional structure with blueshifted and redshifted regions.

Approximately 90% of identified clumps are likely to form low-mass stars.

Evidence supports the collect-and-collapse process triggered by massive star feedback.

Abstract

We performed a multiwavelength study towards HII region Sh2-104. New maps of 12CO J=1-0 and 13CO J=1-0 were obtained from the Purple Mountain Observatory (PMO) 13.7 m radio telescope. Sh2-104 displays a double-ring structure. The outer ring with a radius of 4.4 pc is dominated by 12 um, 500 um, 12CO J=1-0, and 13CO J=1-0 emission, while the inner ring with a radius of 2.9 pc is dominated by 22 um and 21 cm emission. We did not detect CO emission inside the outer ring. The north-east portion of the outer ring is blueshifted, while the south-west portion is redshifted. The present observations have provided evidence that the collected outer ring around Sh2-104 is a two-dimensional structure. From the column density map constructed by the Hi-GAL survey data, we extract 21 clumps. About 90\% of all the clumps will form low-mass stars. A power-law fit to the clumps yields M=281Msun(r/pc)^1.31. The selected YSOs are associated with the collected material on the edge of Sh2-104. The derived dynamical age of Sh2-104 is 1.6*10^6 yr. Compared the Sh2-104 dynamical age with the YSOs timescale and the fragmentation time of the molecular ring, we further confirm that collect-and-collapse process operates in this region, indicating a positive feedback from a massive star for surrounding gas.