Disentangling the galactic and intergalactic components in 313 observed Lyman-alpha line profiles between redshift 0 and 5
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| Main Authors: | , , , , , , , |
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| Format: | Preprint |
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2025
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| _version_ | 1866917412327129088 |
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| author | Gurung-López, Siddhartha Byrohl, Chris Gronke, Max Spinoso, Daniele Torralba, Alberto Fernández-Soto, Alberto Arnalte-Mur, Pablo Martínez, Vicent J. |
| author_facet | Gurung-López, Siddhartha Byrohl, Chris Gronke, Max Spinoso, Daniele Torralba, Alberto Fernández-Soto, Alberto Arnalte-Mur, Pablo Martínez, Vicent J. |
| contents | Lyman-Alpha (Lya) photons emitted in star-forming galaxies undergo complex radiative transfer through the interstellar (ISM), circumgalactic (CGM), and intergalactic medium (IGM), imprinting characteristic signatures on their observed line profiles. We use the open-source package zELDA (redshift Estimator for Line profiles of Distant Lyman-Alpha emitters) to disentangle the galactic and intergalactic contributions in 313 Lya spectra observed with HST/COS and MUSE, spanning 0<z<6. zELDA employs artificial neural networks trained on mock Lya spectra generated with Monte Carlo radiative transfer through thin-shell models and IGM transmission curves from the TNG100 simulation. We find that sources at $z<0.5$ exhibit minimal IGM attenuation, whereas at $z>3$ the IGM significantly suppresses the blue peak of Lya. After correcting for IGM effects, the stacked intrinsic galactic Lya line profiles display remarkably little evolution from $z=0$ to $z=6$. We measure the mean IGM Lya escape fraction, finding $<f^{IGM}_{esc}> > 90\%$ for z<0.5, decreasing from $\sim0.85$ at $z=3$ to $\sim0.55$ at $z=5$. Our measurement of the redshift evolution of the Lya IGM escape fraction agrees with independent constraints on the IGM mean optical depth. After a comparison between our $<f^{IGM}_{esc}>$ estimation and the global Lya escape fraction from the literature, our findings indicate that the IGM might dominate Lya observability at redshift z$\gtrsim$5.0, after which ISM and CGM effects tend to dominate at lower $z$. Our results demonstrate that zELDA enables robust reconstruction of intrinsic Lya spectra and provides a direct probe of the interplay between galactic outflows and IGM transmission across cosmic time. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2503_03824 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Disentangling the galactic and intergalactic components in 313 observed Lyman-alpha line profiles between redshift 0 and 5 Gurung-López, Siddhartha Byrohl, Chris Gronke, Max Spinoso, Daniele Torralba, Alberto Fernández-Soto, Alberto Arnalte-Mur, Pablo Martínez, Vicent J. Astrophysics of Galaxies Lyman-Alpha (Lya) photons emitted in star-forming galaxies undergo complex radiative transfer through the interstellar (ISM), circumgalactic (CGM), and intergalactic medium (IGM), imprinting characteristic signatures on their observed line profiles. We use the open-source package zELDA (redshift Estimator for Line profiles of Distant Lyman-Alpha emitters) to disentangle the galactic and intergalactic contributions in 313 Lya spectra observed with HST/COS and MUSE, spanning 0<z<6. zELDA employs artificial neural networks trained on mock Lya spectra generated with Monte Carlo radiative transfer through thin-shell models and IGM transmission curves from the TNG100 simulation. We find that sources at $z<0.5$ exhibit minimal IGM attenuation, whereas at $z>3$ the IGM significantly suppresses the blue peak of Lya. After correcting for IGM effects, the stacked intrinsic galactic Lya line profiles display remarkably little evolution from $z=0$ to $z=6$. We measure the mean IGM Lya escape fraction, finding $<f^{IGM}_{esc}> > 90\%$ for z<0.5, decreasing from $\sim0.85$ at $z=3$ to $\sim0.55$ at $z=5$. Our measurement of the redshift evolution of the Lya IGM escape fraction agrees with independent constraints on the IGM mean optical depth. After a comparison between our $<f^{IGM}_{esc}>$ estimation and the global Lya escape fraction from the literature, our findings indicate that the IGM might dominate Lya observability at redshift z$\gtrsim$5.0, after which ISM and CGM effects tend to dominate at lower $z$. Our results demonstrate that zELDA enables robust reconstruction of intrinsic Lya spectra and provides a direct probe of the interplay between galactic outflows and IGM transmission across cosmic time. |
| title | Disentangling the galactic and intergalactic components in 313 observed Lyman-alpha line profiles between redshift 0 and 5 |
| topic | Astrophysics of Galaxies |
| url | https://arxiv.org/abs/2503.03824 |