Massive Star Formation at Supersolar Metallicities: Constraints on the Initial Mass Function
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| Main Authors: | , , , , , , , , |
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| Format: | Preprint |
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2025
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| _version_ | 1866908557027311616 |
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| author | Gjergo, Eda Zhang, Zhiyu Kroupa, Pavel Sorokin, Aleksei Yan, Zhiqiang Guo, Ziyi Jerabkova, Tereza Zoonozi, Akram Hasani Haghi, Hosein |
| author_facet | Gjergo, Eda Zhang, Zhiyu Kroupa, Pavel Sorokin, Aleksei Yan, Zhiqiang Guo, Ziyi Jerabkova, Tereza Zoonozi, Akram Hasani Haghi, Hosein |
| contents | Metals enhance the cooling efficiency of molecular clouds, promoting fragmentation. Consequently, increasing the metallicity may boost the formation of low-mass stars. Within the integrated galaxy initial mass function (IGIMF) theory, this effect is empirically captured by a linear relation between the slope of the low-mass stellar IMF, $α_1$, and the metal mass fraction, $Z$. This linear $α_1$-$Z$ relation has been calibrated up to $\approx 2 \, Z_{\odot}$, though higher metallicity environments are known to exist. We show that if the linear $α_1$-$Z$ relation extends to higher metallicities ($[Z] \gtrsim 0.5$), massive star formation is suppressed entirely. Alternatively, fragmentation efficiency may saturate beyond some metallicity threshold if gravitational collapse cascades rapidly enough. To model this behavior, we propose a logistic function describing the transition from metallicity-sensitive to metallicity-insensitive fragmentation regimes. We provide a user-friendly public code, pyIGIMF, which enables the instantaneous computation of the IGIMF theory with the logistic $α_1$-$Z$ relation. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2509_20440 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Massive Star Formation at Supersolar Metallicities: Constraints on the Initial Mass Function Gjergo, Eda Zhang, Zhiyu Kroupa, Pavel Sorokin, Aleksei Yan, Zhiqiang Guo, Ziyi Jerabkova, Tereza Zoonozi, Akram Hasani Haghi, Hosein Astrophysics of Galaxies Metals enhance the cooling efficiency of molecular clouds, promoting fragmentation. Consequently, increasing the metallicity may boost the formation of low-mass stars. Within the integrated galaxy initial mass function (IGIMF) theory, this effect is empirically captured by a linear relation between the slope of the low-mass stellar IMF, $α_1$, and the metal mass fraction, $Z$. This linear $α_1$-$Z$ relation has been calibrated up to $\approx 2 \, Z_{\odot}$, though higher metallicity environments are known to exist. We show that if the linear $α_1$-$Z$ relation extends to higher metallicities ($[Z] \gtrsim 0.5$), massive star formation is suppressed entirely. Alternatively, fragmentation efficiency may saturate beyond some metallicity threshold if gravitational collapse cascades rapidly enough. To model this behavior, we propose a logistic function describing the transition from metallicity-sensitive to metallicity-insensitive fragmentation regimes. We provide a user-friendly public code, pyIGIMF, which enables the instantaneous computation of the IGIMF theory with the logistic $α_1$-$Z$ relation. |
| title | Massive Star Formation at Supersolar Metallicities: Constraints on the Initial Mass Function |
| topic | Astrophysics of Galaxies |
| url | https://arxiv.org/abs/2509.20440 |