Hunting for open clusters inGaiaEDR3: 628 new open clusters found with OCfinder

Abstract

Context.The improvements in the precision of the published data inGaiaEDR3 with respect toGaiaDR2, particularly for parallaxes and proper motions, offer the opportunity to increase the number of known open clusters in the Milky Way by detecting farther and fainter objects that have thus far gone unnoticed.Aims.Our aim is to continue to complete the open cluster census in the Milky Way with the detection of new stellar groups in the Galactic disc. We useGaiaEDR3 up to magnitudeG= 18 mag, increasing the magnitude limit and therefore the search volume explored in one unit with respect to our previous studies.Methods.We used theOCfindermethod to search for new open clusters inGaiaEDR3 using a big data environment. As a first step,OCfinderidentified stellar statistical overdensities in five-dimensional astrometric space (position, parallax, and proper motions) using theDBSCANclustering algorithm. Then, these overdensities were classified into random statistical overdensities or real physical open clusters using a deep artificial neural network trained on well-characterisedG,GBP–GRPcolour-magnitude diagrams.Results.We report the discovery of 628 new open clusters within the Galactic disc, with most of them being located beyond 1 kpc from the Sun. From the estimation of ages, distances, and line-of-sight extinctions of these open clusters, we see that young clusters align following the Galactic spiral arms while older ones are dispersed in the Galactic disc. Furthermore, we find that most open clusters are located at low Galactic altitudes with the exception of a few groups older than 1 Gyr.Conclusions.We show the success of theOCfindermethod leading to the discovery of a total of 1274 open clusters (joining the discoveries here with the previous ones based onGaiaDR2), which represents almost 50% of the known population. Our ability to perform big data searches on a large volume of the Galactic disc, together with the higher precision inGaiaEDR3, enable us to keep completing the census with the discovery of new open clusters.