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Harvard ADS: Revealing Potential Initial Mass Function Variations with Metallicity: JWST Observations of Young Open Clusters in a Low-metallicity Environment

Paper abstract: We present the substellar mass function of star-forming clusters (?0.1 Myr old) in a low-metallicity environment (?-0.7 dex). We performed deep JWST/NIRCam and MIRI imaging of two star-forming clusters in Digel Cloud 2, a star-forming region in the outer Galaxy (R _G ? 15 kpc). The very high sensitivity and spatial resolution of JWST enable us to resolve cluster members clearly down to a mass detection limit of 0.02 M _?, enabling the first detection of brown dwarfs in low-metallicity clusters. A total of 52 and 91 sources were extracted in mass-A _V -limited samples in the two clusters, from which initial mass functions (IMFs) were derived by model-fitting the F200W band luminosity function, resulting in IMF peak masses (hereafter M _C ) for both clusters. Although the uncertainties are rather large, the obtained M _C values are lower than those in any previous study ( ). Comparison with the local open clusters with similar ages to the target clusters (~10⁶–10⁷ yr) suggests a metallicity dependence of M _C , with lower M _C at lower metallicities, while the comparison with globular clusters, with similarly low metallicities but considerably older (~10¹⁰ yr), suggests that the target clusters have not yet experienced significant dynamical evolution and remain in their initial physical condition. The lower M _C is also consistent with the theoretical expectation of the lower Jeans mass owing to the higher gas density under such low metallicity. The M _C values derived from observations in such an environment would place significant constraints on the understanding of star formation.