Exploring Stellar Cluster and Feedback-driven Star Formation in the Galactic Mid-infrared Bubble [HKS2019] E70

Abstract

We present a comprehensive analysis of the Galactic mid-infrared bubble [HKS2019] E70 (E70) by adopting a multiwavelength approach to understand the physical environment and star formation scenario around it. We identified a small (radius ∼1.7 pc) stellar cluster inside the E70 bubble, and its distance is estimated as 3.26 ± 0.45 kpc. This cluster is embedded in the molecular cloud and hosts massive stars, as well as young stellar objects (YSOs), suggesting active star formation in the region. The spectral type of the brightest star (M1) of the E70 cluster is estimated as O9V, and a circular ring/shell of gas and dust is found around it. The diffuse radio emission inside this ring/shell, the excess pressure exerted by the massive star M1 at the YSO’s core, and the distribution of photodissociation regions, a class I YSO, and two ultracompact H ii regions on the rim of this ring/shell clearly suggest positive feedback of the massive star M1 in the region. We also found a low-density shell-like structure in the 12CO(J = 1–0) molecular emission along the perimeter of the E70 bubble. The velocity structure of the 12CO emission suggests that the feedback from the massive star appears to have expelled the molecular material, and the subsequent swept-up material is what appears as the E70 bubble.

Cluster Formation in a Filamentary Cloud: The Case of the Stellar Cluster NGC 2316

“…As this region shows many signatures of star-forming activities, we can expect young populations of stars to be embedded in this region. As these young populations (or YSOs) are usually associated with the circumstellar disk, we identified/classified them based on their excess IR emission (for details, please refer to Verma et al 2023). We found both Class I and Class II YSOs in our selected FOV of this region and their locations are shown in panel (c) of Figure 5.…”

“…To understand the structure of the NGC 2316 cluster, we generated the stellar surface density map of the region by the nearest neighbor method (Gutermuth et al 2005). This was done in a grid having a size of 10″ and for the twentieth nearest star, using the NIR catalog (for details, please refer to Verma et al 2023). We overlaid the estimated isodensity contours (red curves) in Figure 1.…”

“…This kind of morphology is a typical feature of the H II region/MIR bubble created by the massive star/s. (Sharma et al 2007;Pandey et al 2008;Verma et al 2023).…”

Investigating the Star-forming Sites in the Outer Galactic Arm

“…E70-MIR bubble E70, first cataloged by Hanaoka et al (2019). Verma et al (2023b) reported that it is located at a distance of 3.26 kpc, has a small stellar clustering of radius ∼1.7 pc, and is hosting a massive O9V star possessing positive feedback and "collect and collapse scenario" might be a probable star formation scenario at the rim of this bubble. KPS0620-KPS0620 is a poorly studied star cluster that is located at a distance of 6.1 kpc according to Buckner & Froebrich (2013), whereas Kharchenko et al (2013) reported it to be located at 2.2 kpc.…”

“…The system temperature includes noises from the antenna (the optical system, the membrane, and the dome), the receiver, and the atmosphere (Su et al 2019). A subset of this data comprising the E70 bubble has already been presented in Verma et al (2023b). The lowest level value for both the contours is the mean value with a step size of 1σ.…”