Searching for stellar population in the molecular cloud GRSMC 045.49+00.04

TL;DR

This study identifies and characterizes young stellar objects in the G 045.49+00.04 molecular cloud, revealing differences in age, distribution, and evolution between clustered and non-clustered populations, and suggesting triggered star formation.

Contribution

It provides a detailed analysis of YSO populations in a specific molecular cloud, including their distribution, ages, and evolutionary states, highlighting the role of external triggers in star formation.

Findings

1482 YSOs identified with masses 1.5-22 Msol

Cluster YSOs are younger and more evolved than non-cluster YSOs

Star formation likely triggered by shock front from GRS 1915+105

Abstract

Understanding the characteristics of young stellar populations is essential for deriving insights into star formation processes within parent molecular clouds and the influence of massive stars. This study focuses on YSOs in the G 045.49+00.04 molecular cloud, including three UC HII regions. Using infrared photometric data and radiation models, we identified 1482 YSOs with masses ranging from 1.5 to 22 Msol. Among these, 315 form dense clusters near IRAS sources, with high-mass stars responsible for ionization. The non-cluster YSOs (1168) are uniformly distributed on the field. The distribution of YSOs from both samples on the colour-magnitude diagram and by the evolutionary ages is different. About 75% of objects in the IRAS clusters are concentrated around the ZAMS and have a well-defined peak at an age of Log(Age[years]) = 6.75, with a narrow spread. The non-cluster objects have two concentrations located to the right and left of the 0.1 Myr isochrone and two well-defined peaks at Log(Age) = 6.25 and 5.25. The K luminosity functions alpha slopes for the IRAS clusters and non-cluster objects are 0.32 and 0.72, respectively. The steeper alpha slope is suggesting that the non-cluster objects are less evolved, which is well consistent with the evolutionary age. Similar patterns were observed in the neighboring G 45.14+00.14 region. The both regions (G 045.49+00.04 and G 45.14+00.14) are located and distinguished by their brightness and density at the edge of the bubble around the highly variable X-ray binary GRS 1915+105, which includes a black hole and a K-giant companion. Based on the above, we can assume that the process of star formation in the young IRAS clusters was triggered by the GRS 915+105-initiated shock front inside the ISM massive condensation, through the process of "collecting and collapse". Most non-cluster objects probably belong to a later generation.