Victor Almendros Abad, OA Palermo, Italy — May 5, 2025

Brown dwarfs have been extensively studied in nearby star-forming regions (d < 400 pc). However, theories suggest that high gas or stellar densities, as well as the presence of massive OB stars, may enhance brown dwarf formation relative to stars. To test this, it is crucial to study brown dwarf populations in massive young clusters, which provide dramatically different star-forming conditions. The nearest examples of such clusters are the supermassive star clusters (SSCs) Westerlund 1 and Westerlund 2, each exceeding 30000 Msun in total stellar mass.

As part of the EWOCS (Extended Westerlund 1 and 2 Open Clusters Survey) project, we have obtained deep JWST/NIRCam observations of these clusters. A key goal of this project is to derive their mass functions and assess whether extreme environments influence brown dwarf formation. By combining these results with studies of other massive young clusters led by members of the project, such as Trumpler 14 and RCW 38, we are placing the first robust constraints on the efficiency of brown dwarf formation in such environments. In this talk, I will present the JWST/NIRCam data products of both clusters, the (sub)stellar initial mass function of Westerlund 1, and the detection and characterization of brown dwarfs in Westerlund 2, enabled by the rich multi-wavelength filter selection. I will also discuss the implications of these results for our understanding of star formation.