Ammonia mapping observations of the Galactic infrared bubble N49: Three NH$_3$ clumps along the molecular filament

TL;DR

This study maps ammonia emissions in the Galactic infrared bubble N49, revealing three dense clumps with varying temperatures and star formation activity, highlighting the influence of stellar feedback and filament interactions.

Contribution

First NH$_3$ mapping of N49 revealing three dense clumps and their physical conditions, suggesting filament interactions and localized star formation processes.

Findings

Clump B is heated by embedded MYSOs and associated with filament intersection.

Clumps A and C are potential sites of spontaneous star formation.

Filament-filament interaction likely influences dense gas formation.

Abstract

We have carried out the NH$_3$ $(J,K)=(1,1),(2,2),$ and $(3,3)$ mapping observations toward the Galactic infrared bubble N49 (G28.83-0.25) using the Nobeyama 45 m telescope. Three NH$_3$ clumps (A, B, and C) were discovered along the molecular filament with the radial velocities of $\sim$ 96, 87, and 89 km s$^{-1}$, respectively. The kinetic temperature derived from the NH$_3$ (2,2)/NH$_3$ (1,1) shows $T_{\rm kin} = 27.0 \pm 0.6$ K enhanced at Clump B in the eastern edge of the bubble, where position coincides with massive young stellar objects (MYSOs) associated with the 6.7 GHz class II methanol maser source. This result shows the dense clump is locally heated by stellar feedback from the embedded MYSOs. The NH$_3$ Clump B also exists at the 88 km s$^{-1}$ and 95 km s$^{-1}$ molecular filament intersection. We therefore suggest that the NH$_3$ dense gas formation in Clump B can be explained by a filament-filament interaction scenario. On the other hand, NH$_3$ Clump A and C at the northern and southern side of the molecular filament might be the sites of spontaneous star formation because these clumps are located $\sim$5$-$10 pc away from the edge of the bubble.