Study investigates young low-mass stellar population of NGC 1893, detects over 100 new stars
Using the Devasthal Optical Telescope (DOT), Indian astronomers have observed a young star cluster known as NGC 1893. The observational campaign allowed the researchers to investigate hundreds of young low-mass stars in the cluster, resulting in the detection of over 100 new objects of this type. The study was detailed in a paper published November 23 on arXiv.org.
Young star clusters are observed to host young stars of a diverse mass range, formed from the same molecular cloud. However, massive stars in such systems may significantly influence the evolution of low-mass stars and subsequent star formation. When stars in clusters form, they tend to ionize the natal cloud and create an expanding HII region—an area of interstellar ionized atomic hydrogen. Afterward, this expanding HII region interacts with the surrounding cloud and may initiate star formation via various processes.
Therefore, young star clusters associated with HII regions are perceived by astronomers as excellent sites to study the influence of massive stars on the formation and evolution of low-mass stars. These clusters could also shed more light on the various processes involved in triggering star formation.
So a group of researchers led by Neelam Panwar of the Aryabhatta Research Institute of Observational sciencES (ARIES) in India inspected NGC 1893—a young star cluster associated with the HII region designated Sh2-236. At a distance of about 10,500 light years away from the Earth, NGC 1893 contains about five O-type stars and several B-type stars. To date, most studies of this cluster were shallow (about 21-22 mag) and complete up to one solar mass. Panwar's team wanted to change this by conducting deep photometric observations of NGC 1893.
"To characterize the low-mass stars and study star formation in the cluster region, we carried out deep V I band observations of the region with the 4K×4K CCD IMAGER mounted on the 3.6-m Devasthal Optical Telescope (DOT). Our analysis shows that the present optical data are ∼ 3 mag deeper than that of the previous studies," the astronomers wrote in the paper.
The optical data from DOT were deep enough to reveal the stars in NGC 1893 with masses below 0.2 solar masses. The DOT data allowed the team to identify 425 young stars in the central portion of the cluster, out of which 110 turned out to be new findings.
The research found that a majority of the identified objects are low-mass stars with age below 10 million years. Based on the results, the astronomers suggest an insignificant contribution of the field stars in the pre-main sequence (PMS) zone of the cluster's color-magnitude diagram (CMD) and young stellar population of the cluster region can be identified using the CMD.
Furthermore, the slope of the mass function in the mass range between 0.2 and 2.5 solar masses turned out to be approximately -1.43. This result is consistent with values obtained for other known star-forming complexes. The authors of the paper added that the spatial distribution of the investigated young stars in NGC 1893 as a function of mass indicates that toward the cluster center, most of the stars are relatively massive.
More information: Neelam Panwar, Amit Kumar, S. B. Pandey, Deep V and I CCD photometry of young star cluster NGC 1893 with the 3.6m DOT. arXiv:2111.11796v1 [astro-ph.SR], arxiv.org/abs/2111.11796
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