Deep photocurrent observations of the open cluster Bochum 2


Deep optical observations explore the open Bochum Cluster 2

Color composite image of the Bochum 2 cluster region. Three massive stars located within the cluster region are also marked with star symbols along with their spectral type. Credit: Kaur et al, 2023

Indian astronomers have conducted deep optical observations of the Bochum 2 open galaxy cluster using the 1.3-meter Devastal Fast Optical Telescope (DFOT). Results of the monitoring campaign published on May 2 arXivproviding important insights into the characteristics of this group.

Open clusters (OCs), which formed from the same giant molecular cloud, are groups of stars loosely bound gravitationally to each other. To date, more than 1,000 of them have been discovered in the Milky Way, and scientists are still looking for more, hoping to find a variety of these star clusters. Expand the list of known galaxies open groups Studying them in detail could be crucial to improving our understanding of the formation and evolution of our galaxy.

Bochum 2 (or Boc2 for short) is a small OC in the far northern outskirts of a giant star-forming H II region (which contains clouds of ionized atomic hydrogen) known as Sh 2−284. Although Bochum 2 has been known for decades, it is a poorly studied group, and there are many uncertainties regarding its core parameters, such as distance and age estimates, as previous studies were based mainly on shallow photometric data.

Therefore, in order to better characterize Bochum 2, a team of astronomers led by Harmeen Kaur of Kumaun University in Nainital, India, used DFOT to perform a deeper photometry of this cluster. Their study was supplemented with data from Gaia Data Release 3 (DR3).

We performed a deep (V∼21.3 mag) and wide field (field of view ∼18.5 x 18.5 arcmin)2) multi-band optical (UBV Ic) observations about the Boc2 cluster,” the researchers wrote in the paper.

Observations found that the radius of Bochum II is 3.6 light years, while the tidal radius is about 6.4-8.2 times. This indicates that most of the stars in this cluster are remnants of an older group of stars that formed over an earlier era of star formation.

According to the study, the Bochum 2 has a redness of about 0.8 mag and is located around 12,400 mag light years away from Earth. Moreover, the data collected allowed astronomers to identify 24 stars as the most likely members of the group and calculate the age of the most numerous of them. huge stars in Bochum 2, which shifts to about 5 million years old.

When it comes to the slope of the mass function in the mass area, it has been found to be equal to -2.42 in the mass range between 0.72 and 2.8 solar masses. This result indicates the presence of an excessive number of low-mass stars in Bochum-2.

The study also found that Bochum 2 exhibits a mass separation effect as the cluster’s dynamic age, estimated at 8-14 million years, is older than that of massive stars. This discovery seems to confirm that massive stars formed in the inner region of the cluster, in a recent era of star formation.

more information:
Harmin Kaur et al., Structural analysis of the open cluster Bochum II, arXiv (2023). doi: 10.48550/arxiv.2305.01212

Journal information:

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