From atoms to stars: Modelling $\mathrm{H}_2$ formation and its impact on galactic evolution
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arXiv
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| Autori principali: | , , , , |
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| Natura: | Preprint |
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2025
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| _version_ | 1866911187840532480 |
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| author | Lozano, E. Scannapieco, C. Nuza, S. E. Ascasibar, Y. Springel, V. |
| author_facet | Lozano, E. Scannapieco, C. Nuza, S. E. Ascasibar, Y. Springel, V. |
| contents | We present a sub-grid model for star formation in galaxy simulations, incorporating molecular hydrogen ($\mathrm{H}_2$) production via dust grain condensation and its destruction through star formation and photodissociation. Implemented within the magnetohydrodynamical code AREPO, our model tracks the non-equilibrium mass fractions of molecular, ionised, and atomic hydrogen, as well as a stellar component, by solving a system of differential equations governing mass exchange between these phases. Star formation is treated with a variable rate dependent on the local $\mathrm{H}_2$ abundance, which itself varies in a complex way with key quantities such as gas density and metallicity. Testing the model in a cosmological simulation of a Milky Way-mass galaxy, we obtain a well-defined spiral structure at $z = 0$, including a gas disc twice the size of the stellar one, alongside a realistic star formation history. Our results show a broad range of star formation efficiencies per free-fall time, from as low as $0.001\%$ at high redshift to values between $0.1\%$ and $10\%$ for ages $\gtrsim 3-4 \, \mathrm{Gyr}$. These findings align well with observational estimates and simulations of a turbulent interstellar medium. Notably, our model reproduces a star formation rate versus molecular hydrogen surface densities relation akin to the molecular Kennicutt-Schmidt law. Furthermore, we find that the star formation efficiency varies with density and metallicity, providing an alternative to fixed-efficiency assumptions and enabling comparisons with more detailed star formation models. Comparing different star formation prescriptions, we find that in models that link star formation to $\mathrm{H}_2$, star formation onset is $\sim \! 500 \, \mathrm{Myr}$ later than those relying solely on total or cold gas density. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2510_00959 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | From atoms to stars: Modelling $\mathrm{H}_2$ formation and its impact on galactic evolution Lozano, E. Scannapieco, C. Nuza, S. E. Ascasibar, Y. Springel, V. Astrophysics of Galaxies We present a sub-grid model for star formation in galaxy simulations, incorporating molecular hydrogen ($\mathrm{H}_2$) production via dust grain condensation and its destruction through star formation and photodissociation. Implemented within the magnetohydrodynamical code AREPO, our model tracks the non-equilibrium mass fractions of molecular, ionised, and atomic hydrogen, as well as a stellar component, by solving a system of differential equations governing mass exchange between these phases. Star formation is treated with a variable rate dependent on the local $\mathrm{H}_2$ abundance, which itself varies in a complex way with key quantities such as gas density and metallicity. Testing the model in a cosmological simulation of a Milky Way-mass galaxy, we obtain a well-defined spiral structure at $z = 0$, including a gas disc twice the size of the stellar one, alongside a realistic star formation history. Our results show a broad range of star formation efficiencies per free-fall time, from as low as $0.001\%$ at high redshift to values between $0.1\%$ and $10\%$ for ages $\gtrsim 3-4 \, \mathrm{Gyr}$. These findings align well with observational estimates and simulations of a turbulent interstellar medium. Notably, our model reproduces a star formation rate versus molecular hydrogen surface densities relation akin to the molecular Kennicutt-Schmidt law. Furthermore, we find that the star formation efficiency varies with density and metallicity, providing an alternative to fixed-efficiency assumptions and enabling comparisons with more detailed star formation models. Comparing different star formation prescriptions, we find that in models that link star formation to $\mathrm{H}_2$, star formation onset is $\sim \! 500 \, \mathrm{Myr}$ later than those relying solely on total or cold gas density. |
| title | From atoms to stars: Modelling $\mathrm{H}_2$ formation and its impact on galactic evolution |
| topic | Astrophysics of Galaxies |
| url | https://arxiv.org/abs/2510.00959 |