Propagation of Highly Efficient Star Formation in NGC 7000

TL;DR

This study investigates the properties and star formation activities of molecular clumps in NGC 7000, revealing that star formation efficiency is enhanced near the HII region boundary, likely due to triggered star formation.

Contribution

It provides detailed observations of NH3 and H2O masers in NGC 7000, linking star formation activity to the geometry of the HII region and suggesting triggered star formation enhances efficiency.

Findings

Five NH3 clumps identified with sizes 0.2-1 pc and masses 9-452 M_sun.

Star formation activity varies among clumps, related to their position relative to the HII region.

Clump near the HII boundary shows high star formation efficiency of 36-62%.

Abstract

We surveyed the (1,1), (2,2), and (3,3) lines of NH3 and the H2O maser toward the molecular cloud L935 in the extended HII region NGC 7000 with an angular resolution of 1.6' using the Kashima 34-m telescope. We found five clumps in the NH3 emission with a size of 0.2--1 pc and mass of 9--452 M_sun. The molecular gas in these clumps has a similar gas kinetic temperature of 11--15 K and a line width of 1--2 km/s. However, they have different star formation activities such as the concentration of T-Tauri type stars and the association of H2O maser sources. We found that these star formation activities are related to the geometry of the HII region. The clump associated with the T-Tauri type star cluster has a high star formation efficiency of 36--62%. This clump is located near the boundary of the HII region and molecular cloud. Therefore, we suggest that the star formation efficiency increases because of the triggered star formation.