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Arxiv: MIDIS: Unveiling the Role of Strong Ha-emitters during the Epoch of Reionization with JWST Published: 9/27/2023 5:13:08 PM Updated: 4/23/2024 12:38:41 PM

Paper abstract: By using the ultra-deep \textit{JWST}/MIRI image at 5.6 \mu m in the HubbleeXtreme Deep Field, we constrain the role of strong H\alpha-emitters (HAEs)during Cosmic Reionization at z~eq7-8. Our sample of HAEs is comprised ofyoung (<35\;\rm Myr) galaxies, except for one single galaxy (~300\;\rm Myr), with low stellar masses (<~ 10^{9}\;\rm M_{\odot}).These HAEs show a wide range of UV-\beta slopes, with a median value of\beta = -2.15\pm0.21 which broadly correlates with stellar mass. We estimatethe ionizing photon production efficiency (\xi_{ion,0}) of these sources(assuming f_{esc,LyC} = 0\%), which yields a median value \rmlog_{10}(\xi_{ion,0}/(Hz\;erg^{-1})) = 25.50^{+0.10}_{-0.12}. We show that\xi_{ion,0} positively correlates with EW_{0}(H\alpha) and specific starformation rate (sSFR). Instead \xi_{ion,0} weakly anti-correlates withstellar mass and \beta. Based on the \beta values, we predict f_{esc,LyC}=4\%^{+3}_{-2}, which results in \rm log_{10}(\xi_{ion}/(Hz\;erg^{-1})) =25.55^{+0.11}_{-0.13}. Considering this and related findings from theliterature, we find a mild evolution of \xi_{ion}with redshift. Additionally,our results suggest that these HAEs require only modest escape fractions(f_{esc, rel}) of 6-15\% to reionize their surrounding intergalacticmedium. By only considering the contribution of these HAEs, we estimated theirtotal ionizing emissivity (\dot{N}_{ion}) as \dot{N}_{ion} = 10^{50.53 \pm0.45}; \text{s}^{-1}\text{Mpc}^{-3}. When comparing their \dot{N}_{ion} with"non-H\alpha emitter" galaxies across the same redshift range, we find thatthat strong, young, and low-mass emitters may have played an important roleduring Cosmic Reionization.