Disentangling the galactic and intergalactic components in 313 observed Lyman-alpha line profiles between redshift 0 and 5

Le résumé fourni par la source

Lyman-Alpha (Ly α ) 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 (redshift Estimator for Line profiles of Distant Lyman-Alpha emitters) to disentangle the galactic and intergalactic contributions in 313 Ly α spectra observed with HST/COS and MUSE, spanning 0 < z < 6 . employs artificial neural networks trained on mock Ly α 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 Ly α . After correcting for IGM effects, the stacked intrinsic galactic Ly α line profiles display remarkably little evolution from z = 0 to z = 6 . We measure the mean IGM Ly α escape fraction, finding ⟨ f e s c I G M ⟩ > 90 % for z < 0.5 , decreasing from ∼ 0.85 at z = 3 to ∼ 0.55 at z = 5 . Our measurement of the redshift evolution of the Ly α IGM escape fraction agrees with independent constraints on the IGM mean optical depth. After a comparison between our ⟨ f e s c I G M ⟩ estimation and the global Ly α escape fraction from the literature, our findings indicate that the IGM might dominate Ly α observability at redshift z ≳ 5.0 , after which ISM and CGM effects tend to dominate at lower z . Our results demonstrate that enables robust reconstruction of intrinsic Ly α spectra and provides a direct probe of the interplay between galactic outflows and IGM transmission across cosmic time.

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