MIDIS: Unveiling the Role of Strong Hα Emitters During the Epoch of Reionization with JWST
Abstract
By using an ultradeep 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 Myr) galaxies, except for one single galaxy (≈300 Myr), with low stellar masses (≲109 M ⊙). These HAEs show a wide range of rest-frame UV continuum slopes (β), with a median value of β = ‑2.15 ± 0.21, which broadly correlates with stellar mass. We estimate the ionizing photon production efficiency (ξ ion,0) of these sources (assuming f esc,LyC = 0%), which yields a median value . We show that ξ ion,0 positively correlates with Hα equivalent width and specific star formation rate. Instead ξ ion,0 weakly anticorrelates with stellar mass and β. Based on the β values, we predict , which results in . Considering this and related findings from the literature, we find a mild evolution of ξ 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 intergalactic medium. By only considering the contribution of these HAEs, we estimated their total ionizing emissivity ( ) as . When comparing their with non-HAE 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.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- July 2024
- DOI:
- 10.3847/1538-4357/ad4147
- arXiv:
- arXiv:2309.15671
- Bibcode:
- 2024ApJ...969...12R
- Keywords:
-
- Galaxy formation;
- Reionization;
- Starburst galaxies;
- Galaxy evolution;
- High-redshift galaxies;
- Star formation;
- James Webb Space Telescope;
- 595;
- 1383;
- 1570;
- 594;
- 734;
- 1569;
- 2291;
- Astrophysics - Astrophysics of Galaxies;
- Astrophysics - Cosmology and Nongalactic Astrophysics
- E-Print:
- 21 pages, 11 Figures, 1 table. Accepted for publication in ApJ. Updated version 13/06/2024 -- found a mistake in the reported eq. 2 (now corrected)