| Name: | Anindya Saha |
| Affiliation: | Indian Institute of Space Science and Technology |
| Conference ID: | ASI2025_368 |
| Title: | Direct observational evidence of multi-epoch massive star formation in G24.47+0.49 |
| Authors: | Anindya Saha 1, Anandmayee Tej 1 |
| Authors Affiliation: | 1 Anindya Saha, Anandmayee Tej Indian Institute of Space Science and Technology, Thiruvananthapuram 695547, Kerala, India |
| Mode of Presentation: | Oral |
| Abstract Category: | Stars, Interstellar Medium, and Astrochemistry in Milky Way |
| Abstract: | Massive stars play a crucial role in the dynamical and chemical evolution of their environment by feeding the ambient interstellar medium (ISM) with material and radiation, especially during its formation stages and late evolutionary phases. This feedback is believed to regulate star formation activities in their vicinity. With their intense UV radiation, massive stars can ionize the surrounding ISM and form HII regions. The expansion of the HII regions leads to two contrasting scenarios: it can either hinder or promote star formation activity in molecular clouds. On the one hand, it can disrupt the natal cloud and inhibit future star formation processes, and on the other hand, this feedback can sweep up surrounding material into dense shells, creating massive fragments that eventually collapse to form subsequent generations of stars at their peripheries. Several studies have found observational evidence of this triggered star formation linking two generations of stars: the ionizing star and the newly formed stars at the peripheries of expanding HII regions. However, gathering evidence for triggered star formation linking multiple epochs of stars around HII regions is challenging as it is difficult to associate evolved massive stars with the next epoch of star-forming regions, each of which must show indications of ongoing star formation activity. As a result, evidence for hierarchical triggering and multi-generation star formation is scarce.
In this talk, I will present our study of ring-like HII region G24.47+0.49 using ALMA data from the ATOMS survey and archival VLA 4.86 GHz data. Our analysis reveals an interesting scenario of hierarchical triggering relating three epochs of massive star formation in concentric rings of the HII region. Through detailed molecular gas kinematics analysis, we unveiled, by far for the first time, direct and unambiguous detection of an expanding outer molecular ring encircling the HII region. |
