BSEC method for unveiling open clusters and its application to Gaia DR3: 83 new clusters

Abstract

Open clusters (OCs) are common in the Milky Way, but most of them remain undiscovered. There are numerous techniques (e.g., machine-learning algorithms) available for the exploration of OCs. However, each method has its limitations and therefore, different approaches to discovering OCs hold significant value. We develop a comprehensive approach method to automatically explore the data space and identify potential OC candidates with relatively reliable membership determination. This approach combines the techniques of HDBSCAN, GMM, and a novel cluster member identification technique, color excess constraint. The new method exhibits efficiency in detecting OCs while ensuring precise determination of cluster memberships. It is called Blind Search-Extra Constraint (BSEC) method. It is successfully applied to the Gaia DR3, and 83 new OCs are found. This study also reports 621 new OC candidates with discernible main sequence or red giant branch. The BSEC technique can discard some false negatives of previous works, which takes about 3 percentage of known clusters. As an extra constraint, color excess (or 2-color) constraint is useful for removing fake cluster member stars from the clusters that are identified from the positions and proper motions of stars, and getting more precise CMDs, when differential reddening of member stars of a cluster is not large (e.g., \DeltaE(G_BP -G_RP)<0.5 mag). It makes the CMDs of 15 percent clusters clearer (in particular for the region near turnoff) and therefore is helpful for CMD and stellar population studies. Our result suggests that color excess constraint is more appropriate for clusters with small differential reddening, such as globular clusters or older OCs, and clusters that the distances of member stars cannot be determined accurately.