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Literature
Date: 4/19/2024

Arxiv: Quantifying the escape of Lyα at z\approx 5-6: a census of Lyα escape fraction with Hα emitting galaxies spectroscopically confirmed by JWST and VLT/MUSE Published: 1/17/2024 9:00:01 PM Updated: 4/18/2024 8:57:24 PM

Paper abstract: JWST provides an unprecedented opportunity for unbiased surveys ofH\alpha-emitting galaxies at z>4 with the NIRCam wide-field slitlessspectroscopy (WFSS). In this work, we present a census of Ly\alpha escapefraction (f_{esc, Ly\alpha}) of 165 star-forming galaxies at z=4.9-6.3using their H\alpha emission directly measured from FRESCO NIRCam/WFSS data.We search for Ly\alpha emission of each H\alpha-emitting galaxy in VLT/MUSEdata. The overall f_{esc, Ly\alpha} measured by stacking is f_{esc,Ly\alpha} is 0.090\pm0.006. We find that f_{esc, Ly\alpha} displays astrong dependence on the observed UV slope (\beta_{\rm obs}) and E(B-V), suchthat the bluest galaxies (\beta_{\rm obs}~-2.5) have the largest escapefractions (f_{\rm esc, Ly\alpha}~0.6), indicative of the crucial roleof dust and gas in modulating the escape of Ly\alpha photons. f_{esc,Ly\alpha} is less well related to other parameters, including the UVluminosity and stellar mass, and the variation in f_{esc, Ly\alpha} with themcan be explained by their underlying coupling with E(B-V) or \beta_{\rm obs}.Our results suggest a tentative decline in f_{esc, Ly\alpha} at z\gtrsim 5,implying increasing intergalactic medium attenuation towards higher redshift.Furthermore, the dependence of f_{esc, Ly\alpha} on \beta_{\rm obs} isproportional to that of the ionizing photon escape fraction (f_{\rm esc,LyC}), indicating the escape of Ly\alpha and ionizing photon may beregulated by similar physical processes. With f_{esc, Ly\alpha} as a proxy tof_{\rm esc, LyC}, we infer that UV-faint (M_{\rm UV}>-16) galaxiescontribute >70\% of the total ionizing emissivity at z=5-6. If theserelations hold during the epoch of reionization, UV-faint galaxies cancontribute the majority of UV photon budget to reionize the Universe.