The SPHINX public data release. II. Using low-ionisation absorption lines and dust attenuation to predict Lyman continuum escape
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2026
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| author | Mauerhofer, Valentin Blaizot, Jérémy Garel, Thibault Verhamme, Anne Gazagnes, Simon Kerutt, Josephine Michel-Dansac, Leo Parker, Kaelee S. Rosdahl, Joakim Saldana-Lopez, Alberto Trebitsch, Maxime Kimm, Taysun Ocvirk, Pierre Teyssier, Romain |
| author_facet | Mauerhofer, Valentin Blaizot, Jérémy Garel, Thibault Verhamme, Anne Gazagnes, Simon Kerutt, Josephine Michel-Dansac, Leo Parker, Kaelee S. Rosdahl, Joakim Saldana-Lopez, Alberto Trebitsch, Maxime Kimm, Taysun Ocvirk, Pierre Teyssier, Romain |
| contents | Low-ionisation state (LIS) absorption lines, such as SiII 1526, are widely used to trace the properties of the interstellar medium (ISM) in galaxies. These lines provide crucial insights into galaxy evolution, including feedback mechanisms, metal enrichment, and the escape fraction of ionising photons ($f_{\rm{esc}}$). We expand our understanding of LIS absorption lines as diagnostic tools for ISM properties and $f_{\rm{esc}}$. Using the SPHINX20 cosmological radiation-hydrodynamics simulation, we generated a comprehensive synthetic dataset of LIS absorption lines and tested their predictive power for $f_{\rm{esc}}$ in star-forming galaxies. Synthetic SiII 1260 and SiII 1526 lines were computed with the radiative transfer code RASCAS, incorporating resonant scattering of photons, fluorescent emission, and interactions with dust grains. The simulated data enhance the public SPHINX20 dataset with high-resolution LIS lines for the full 1380 galaxies and ten viewing angles per galaxy. We analysed correlations between line properties, dust attenuation, and $f_{\rm{esc}}$. We also tested our predictions on observed data using the LzLCS and CLASSY surveys. We found a strong correlation between the dust-corrected residual flux of SiII 1526, $\tilde{R} \equiv \rm{R_{flux}^{1526}} \cdot 10^{-0.4A_{1500}}$, and $f_{\rm{esc}}$. We found $f_{\rm{esc}} \approx 1.041\tilde{R}^{1.887} - 0.002$, with small error bars. When we applied observational conditions, the error increased, but the escape fraction was still well recovered. We show by applying common tools for fitting the spectral energy distribution to our mock data that the inferred dust attenuation is often far from the correct value, with an underestimation of the attenuation when the effect of dust is strongest. Our results demonstrate that the residual flux of SiII 1526 is a powerful predictor of the escape fraction of ionising photons. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2603_17046 |
| institution | arXiv |
| publishDate | 2026 |
| record_format | arxiv |
| spellingShingle | The SPHINX public data release. II. Using low-ionisation absorption lines and dust attenuation to predict Lyman continuum escape Mauerhofer, Valentin Blaizot, Jérémy Garel, Thibault Verhamme, Anne Gazagnes, Simon Kerutt, Josephine Michel-Dansac, Leo Parker, Kaelee S. Rosdahl, Joakim Saldana-Lopez, Alberto Trebitsch, Maxime Kimm, Taysun Ocvirk, Pierre Teyssier, Romain Astrophysics of Galaxies Low-ionisation state (LIS) absorption lines, such as SiII 1526, are widely used to trace the properties of the interstellar medium (ISM) in galaxies. These lines provide crucial insights into galaxy evolution, including feedback mechanisms, metal enrichment, and the escape fraction of ionising photons ($f_{\rm{esc}}$). We expand our understanding of LIS absorption lines as diagnostic tools for ISM properties and $f_{\rm{esc}}$. Using the SPHINX20 cosmological radiation-hydrodynamics simulation, we generated a comprehensive synthetic dataset of LIS absorption lines and tested their predictive power for $f_{\rm{esc}}$ in star-forming galaxies. Synthetic SiII 1260 and SiII 1526 lines were computed with the radiative transfer code RASCAS, incorporating resonant scattering of photons, fluorescent emission, and interactions with dust grains. The simulated data enhance the public SPHINX20 dataset with high-resolution LIS lines for the full 1380 galaxies and ten viewing angles per galaxy. We analysed correlations between line properties, dust attenuation, and $f_{\rm{esc}}$. We also tested our predictions on observed data using the LzLCS and CLASSY surveys. We found a strong correlation between the dust-corrected residual flux of SiII 1526, $\tilde{R} \equiv \rm{R_{flux}^{1526}} \cdot 10^{-0.4A_{1500}}$, and $f_{\rm{esc}}$. We found $f_{\rm{esc}} \approx 1.041\tilde{R}^{1.887} - 0.002$, with small error bars. When we applied observational conditions, the error increased, but the escape fraction was still well recovered. We show by applying common tools for fitting the spectral energy distribution to our mock data that the inferred dust attenuation is often far from the correct value, with an underestimation of the attenuation when the effect of dust is strongest. Our results demonstrate that the residual flux of SiII 1526 is a powerful predictor of the escape fraction of ionising photons. |
| title | The SPHINX public data release. II. Using low-ionisation absorption lines and dust attenuation to predict Lyman continuum escape |
| topic | Astrophysics of Galaxies |
| url | https://arxiv.org/abs/2603.17046 |