Abstract

Contributed Talk - Splinter GalaxyEvol

Thursday, 12 September 2024, 15:24   (S21)

Obscured star clusters in the Inner Milky Way. How many massive young clusters are still awaiting detection?

Akash Gupta, Valentin Ivanov, Thomas Preibisch, Dante Minniti
LMU Munich/ESO/Ph1

Context: The Milky Way star clusters provide important clues for the history of the star formation in our Galaxy. However, the dust in the disk and the innermost regions hides them from the observers. Aims: Our goal is twofold. First, to detect new clusters – we apply the newest methods for detecting clustering with the best available wide-field sky surveys in the mid-infrared because they are the least affected by extinction. Second, we address the question of cluster detection’s completeness, for now limiting it to the most massive star clusters. Methods: This search is based on the mid-infrared Galactic Legacy Infrared Mid-Plane Survey Extraordinaire (GLIMPSE), to minimize the effect of dust extinction. The search Ordering Points To Identify the Clustering Structure (OPTICS) clustering algorithm is applied to identify clusters, after excluding the bluest, presumably foreground sources, to improve the cluster-to-field contrast. The success rate for cluster identification is estimated with a semi-empirical simulation that adds clusters, based on the real objects, to the point source catalog, to be recovered later with the same search algorithm used in the search for new cluster candidates. As a first step, this is limited to the most massive star clusters with a total mass of ∼104 M_sun. Results: Our automated search, combined with inspection of the color-magnitude diagrams and images yielded 659 cluster candidates; 106 of these appear to have been previously identified, suggesting that a large hidden population of star clusters still exists in the inner Milky Way. However, the search for the simulated supermassive clusters achieves a recovery rate of 70-95 %, depending on the distance and extinction toward them. Conclusions: The new candidates – if confirmed – indicate that the Milky Way still harbors a sizeable population of still unknown clusters. However, they must be objects of modest richness, because our simulation indicates that there is no substantial hidden population of supermassive clusters in the central region of our Galaxy.