Quantifying the Escape of Ly α at z ≈ 5–6: A Census of Ly α Escape Fraction with H α -emitting Galaxies Spectroscopically Confirmed by JWST and VLT/MUSE

Lin, X; Cai, Z; Wu, Y; Li, Z; Sun, F; Fan, X; Chen, Z; Li, M; Bian, F; Ning, Y; Jiang, L; Bruzual, G; Charlot, S; Chevallard, J

Journal article

Quantifying the Escape of Ly α at z ≈ 5–6: A Census of Ly α Escape Fraction with H α -emitting Galaxies Spectroscopically Confirmed by JWST and VLT/MUSE

Abstract:: The James Webb Space Telescope provides an unprecedented opportunity for unbiased surveys of Hα-emitting galaxies at z > 4 with the NIRCam's wide-field slitless spectroscopy (WFSS). In this work, we present a census of Lyα escape fraction (f esc,Lyα ) of 165 star-forming galaxies at z = 4.9–6.3, utilizing their Hα emission directly measured from FRESCO NIRCam/WFSS data. We search for Lyα emission of each Hα-emitting galaxy in the Very Large Telescope/MUSE data. The overall f esc,Lyα measured by stacking is 0.090 ± 0.006. We find that f esc,Lyα displays a strong dependence on the observed UV slope (β obs) and E(B − V), such that the bluest galaxies (β obs ∼ −2.5) have the largest escape fractions (f esc,Lyα ≈ 0.6), indicative of the crucial role of dust and gas in modulating the escape of Lyα photons. f esc,Lyα is less well related to other parameters, including the UV luminosity and stellar mass, and the variation in f esc,Lyα with them can be explained by their underlying coupling with E(B − V) or β obs. Our results suggest a tentative decline in f esc,Lyα at z ≳ 5, implying increasing intergalactic medium attenuation toward higher redshift. Furthermore, the dependence of f esc,Lyα on β obs is proportional to that of the ionizing photon escape fraction (f esc,LyC), indicating that the escape of Lyα and ionizing photon may be regulated by similar physical processes. With f esc,Lyα as a proxy to f esc,LyC, we infer that UV-faint (M UV > −16) galaxies contribute >70% of the total ionizing emissivity at z = 5–6. If these relations hold during the epoch of reionization, UV-faint galaxies can contribute the majority of UV photon budget to reionize the Universe.

Publication status:: Published

Peer review status:: Peer reviewed

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APA Style

Lin, X., Cai, Z., Wu, Y., Li, Z., Sun, F., Fan, X., Chen, Z., Li, M., Bian, F., Ning, Y., Jiang, L., Bruzual, G., Charlot, S., & Chevallard, J. (2024). Quantifying the Escape of Ly α at z ≈ 5–6: A Census of Ly α Escape Fraction with H α -emitting Galaxies Spectroscopically Confirmed by JWST and VLT/MUSE. The Astrophysical Journal: Supplement Series, 272(2).

MLA Style

Lin, X, et al. “Quantifying the Escape of Ly α at z ≈ 5–6: A Census of Ly α Escape Fraction with H α -Emitting Galaxies Spectroscopically Confirmed by JWST and VLT/MUSE.” The Astrophysical Journal: Supplement Series, vol. 272, no. 2, 2024.

Chicago Style

Lin, X, Z Cai, Y Wu, et al. 2024. “Quantifying the Escape of Ly α at z ≈ 5–6: A Census of Ly α Escape Fraction with H α -Emitting Galaxies Spectroscopically Confirmed by JWST and VLT/MUSE.” The Astrophysical Journal: Supplement Series 272 (2).
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