DISENTANGLING THE GALACTIC AND INTERGALACTIC COMPONENTS IN 313 OBSERVED LYMAN-ALPHA LINE PROFILES BETWEEN REDSHIFT 0 AND 5

Lyman-Alpha (Lyα) photons emitted in star-forming galaxies undergo complex radiative transfer through the interstellar (ISM), circumgalactic (CGM), and intergalactic medium (IGM), imprinting characteristic sig-natures 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 Lyα spectra observed with HST/COS and MUSE, spanning 0 < z < 6. zELDA employs artificial neural net-works trained on mock Lyα 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 Lyα. After correcting for IGM effects, the stacked intrinsic galactic Lyα line profiles display remarkably little evolution from z = 0 to z = 6. We measure the mean IGM Lyα escape fraction, finding ⟨ fesc4Å ⟩ > 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 Lyα IGM escape fraction agrees with independent constraints on the IGM mean optical depth. After a comparison between our ⟨ fesc4Å ⟩ estimation and the global Lyα escape fraction from the literature, our findings indicate that the IGM might dominate Lyα observability at redshift z≳5.0, after which ISM and CGM effects tend to dominate at lower z. Our results demonstrate that zELDA enables robust reconstruction of intrinsic Lyα spectra and provides a direct probe of the interplay between galactic outflows and IGM transmission across cosmic time.