Isolating the pre-main sequence in Collinder34, NGC3293, NGC3766 and NG6231

TL;DR

This study uses decontaminated 2MASS photometry to analyze four nearby embedded clusters, revealing detached pre-main sequences and suggesting sequential star formation, with some clusters possibly evolving into OB associations.

Contribution

It provides detailed structural and evolutionary analysis of four clusters, highlighting the presence of detached pre-main sequences and their implications for star formation processes.

Findings

Detached pre-main sequences observed in all clusters.

Different radial distributions for pre-main and main sequences.

NGC3766 and NGC6231 may evolve into OB associations.

Abstract

We employed field star decontaminated 2MASS photometry to study four nearby optical embedded clusters -- Collinder34, NGC3293, NGC3766 and NGC6231 -- obtaining deep colour-magnitude diagrams and stellar radial density profiles. We found what seems to be pre-main sequences detached in different amounts from main sequences in these diagrams. The structural analysis of each cluster revealed different radial distributions for these two sequences. We argued that the detached evolutionary sequences in our sample may be evidence of sequential star formation. Finally, we compared the sample cluster parameters with those of other young clusters in the literature and point out evidence that NGC3766 and NGC6231 might be evolving to OB associations.