Interactions of the Infrared bubble N4 with the surroundings

TL;DR

This study investigates the dust properties and interactions of the infrared bubble N4 with its surroundings, exploring the potential for star formation triggered by the bubble's expansion using Herschel data.

Contribution

It provides detailed dust property analysis of N4 and identifies signs of influence on surroundings, contributing to understanding triggered star formation mechanisms.

Findings

Six dust clumps identified around N4 with specific physical properties.

Clear signatures of HII region influence on surrounding environment.

Hints of star formation activity, but further confirmation needed.

Abstract

The physical mechanisms that induce the transformation of a certain mass of gas in new stars are far from being well understood. Infrared bubbles associated with HII regions have been considered to be good samples of investigating triggered star formation. In this paper we report on the investigation of the dust properties of the infrared bubble N4 around the HII region G11.898+0.747, analyzing its interaction with its surroundings and star formation histories therein, with the aim of determining the possibility of star formation triggered by the expansion of the bubble. Using Herschel PACS and SPIRE images with a wide wavelength coverage, we reveal the dust properties over the entire bubble. Meanwhile, we are able to identify six dust clumps surrounding the bubble, with a mean size of 0.50 pc, temperature of about 22 K, mean column density of 1.7 $\times10^{22}$ cm$^{-2}$, mean volume density of about 4.4 $\times10^{4}$ cm$^{-3}$, and a mean mass of 320 $M_{\odot}$. In addition, from PAH emission seen at 8 $\mu$m, free-free emission detected at 20 cm and a probability density function in special regions, we could identify clear signatures of the influence of the HII region on the surroundings. There are hints of star formation, though further investigation is required to demonstrate that N4 is the triggering source.