Unraveling the Feedback-Regulated Star Formation Activities around the Expanding Galactic MIR Bubble [HKS2019] E71

TL;DR

This study investigates the physical environment and star formation activities around the Galactic MIR bubble [HKS2019] E71, revealing feedback-driven expansion and potential triggered star formation via the collect and collapse process.

Contribution

It provides a multi-wavelength analysis of E71, demonstrating feedback effects from a massive star and proposing the collect and collapse mechanism for ongoing star formation.

Findings

Identification of a stellar cluster with a massive star 'm2' at the bubble's center

Evidence of molecular gas expansion and feedback shaping the bubble

Possible triggered star formation through the collect and collapse process

Abstract

We explore the physical environment of the Galactic mid-infrared (MIR) bubble [HKS2019] E71 (hereafter E71) through a multi-wavelength approach. E71 is located at the edge of a filamentary structure, as traced in Herschel images (250-500 $\mu$m), Herschel column density map, and molecular maps in the velocity range [-20,-14] km/s. It hosts a stellar cluster (radius~1.26 pc, distance~1.81+/-0.15 kpc) associated with radio continuum emission, including a centrally positioned B1.5-type massive star (hereafter 'm2'), along with an enhanced population of evolved low-mass stars and young stellar objects. MIR images and molecular line maps reveal a PDR surrounding 'm2', exhibiting an arc-like structure along the edges of E71. Regularly spaced molecular and dust condensations are identified along this structure. The position-velocity map of 12CO emission suggests an expansion of molecular gas concentrated at the periphery of E71. Near-infrared spectroscopic observations with TANSPEC confirm the presence of the accretion process in a massive young stellar object (MYSO) located near the edge of the bubble. High-resolution uGMRT radio continuum maps uncover substructures in the ionized emission, both toward the MYSO and the center of E71. These findings support that 'm2' has shaped an arc-like morphology through its feedback processes. The pressure exerted by 'm2' and the velocity structure of the 12/13CO(1-0) emission suggest that the stellar feedback has likely driven out molecular material, leading to the formation of the expanding E71 bubble. Our overall investigation infers that the "collect and collapse" process might be a possible mechanism that can describe the ongoing star formation activities around the E71 bubble.