2023/09/27 by Rinaldi, P., Caputi, K. I., Iani, E. +40 · 1 citation
#Astrophysics of Galaxies (astro-ph.GA) #Cosmology and Nongalactic Astrophysics (astro-ph.CO) #FOS: Physical sciences
paper · doi:10.48550/arxiv.2309.15671
By using the ultra-deep JWST/MIRI image at 5.6 μm in the Hubble eXtreme Deep Field, we constrain the role of strong Hα-emitters (HAEs) during Cosmic Reionization at z≃7-8. Our sample of HAEs is comprised of young (<35 \rm Myr) galaxies, except for one single galaxy (≈ 300 \rm Myr), with low stellar masses (\lesssim 109 \rm M\odot). These HAEs show a wide range of UV-β slopes, with a median value of β= -2.15±0.21 which broadly correlates with stellar mass. We estimate the ionizing photon production efficiency (ξion,0) of these sources (assuming fesc,LyC = 0%), which yields a median value \rm log10(ξion,0/(Hz erg-1)) = 25.50+0.10-0.12. We show that ξion,0 positively correlates with EW0(Hα) and specific star formation rate (sSFR). Instead ξion,0 weakly anti-correlates with stellar mass and β. Based on the β values, we predict fesc, LyC=4%+3-2, which results in \rm log10(ξion/(Hz erg-1)) = 25.55+0.11-0.13. Considering this and related findings from the literature, we find a mild evolution of ξionwith redshift. Additionally, our results suggest that these HAEs require only modest escape fractions (fesc, rel) of 6-15% to reionize their surrounding intergalactic medium. By only considering the contribution of these HAEs, we estimated their total ionizing emissivity (Nion) as Nion = 1050.53 ± 0.45; s-1Mpc-3. When comparing their Nion with "non-Hα emitter" galaxies across the same redshift range, we find that that strong, young, and low-mass emitters may have played an important role during Cosmic Reionization.