| Autor: |
Chikako Yasui, Natsuko Izumi, Masao Saito, Ryan M. Lau, Naoto Kobayashi, Michael E. Ressler |
| Jazyk: |
angličtina |
| Rok vydání: |
2024 |
| Předmět: |
|
| Zdroj: |
The Astrophysical Journal, Vol 975, Iss 1, p 152 (2024) |
| Druh dokumentu: |
article |
| ISSN: |
1538-4357 |
| DOI: |
10.3847/1538-4357/ad73a2 |
| Popis: |
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 ) $\mathrm{log}{M}_{C}/{M}_{\odot }\simeq -1.5\pm 0.5$ for both clusters. Although the uncertainties are rather large, the obtained M _C values are lower than those in any previous study ( $\mathrm{log}{M}_{C}/{M}_{\odot }\sim -0.5$ ). Comparison with the local open clusters with similar ages to the target clusters (∼10 ^6 –10 ^7 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 (∼10 ^10 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. |
| Databáze: |
Directory of Open Access Journals |
| Externí odkaz: |
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