MIDIS: Strong (Hβ+[O iii]) and Hα Emitters at Redshift z ≃ 7–8 Unveiled with JWST NIRCam and MIRI Imaging in the Hubble eXtreme Deep Field

Rinaldi, P.; Caputi, K. I.; Costantin, L.; Gillman, S.; Iani, E.; Pérez-González, P. G.; Östlin, G.; Colina, L.; Greve, T. R.; Noorgard-Nielsen, H. U.; Wright, G. S.; Alonso-Herrero, A.; Álvarez-Márquez, J.; Eckart, A.; García-Marín, M.; Hjorth, J.; Ilbert, O.; Kendrew, S.; Labiano, A.; Le Fèvre, O.; Pye, J.; Tikkanen, T.; Walter, F.; van der Werf, P.; Ward, M.; Annunziatella, M.; Azzollini, R.; Bik, A.; Boogaard, L.; Bosman, S. E. I.; Gómez, A. Crespo; Jermann, I.; Langeroodi, D.; Melinder, J.; Meyer, R. A.; Moutard, T.; Peissker, F.; Topinka, M.; van Dishoeck, E.; Güdel, M.; Henning, Th.; Lagage, P.-O.; Ray, T.; Vandenbussche, B.; Waelkens, C.; Navarro-Carrera, R.; Kokorev, V.

Abstract

We make use of JWST medium-band and broadband NIRCam imaging, along with ultradeep MIRI 5.6 μm imaging, in the Hubble eXtreme Deep Field to identify prominent line emitters at z ≃ 7–8. Out of a total of 58 galaxies at z ≃ 7–8, we find 18 robust candidates (≃31%) for (Hβ + [O iii]) emitters, based on their enhanced fluxes in the F430M and F444W filters, with EW0(Hβ +[O iii]) ≃87–2100 Å. Among these emitters, 16 lie in the MIRI coverage area and 12 exhibit a clear flux excess at 5.6 μm, indicating the simultaneous presence of a prominent Hα emission line with EW0(Hα) ≃200–3000 Å. This is the first time that Hα emission can be detected in individual galaxies at z > 7. The Hα line, when present, allows us to separate the contributions of Hβ and [O iii] to the (Hβ +[O iii]) complex and derive Hα-based star formation rates (SFRs). We find that in most cases [O iii]/Hβ > 1. Instead, two galaxies have [O iii]/Hβ < 1, indicating that the NIRCam flux excess is mainly driven by Hβ. Most prominent line emitters are very young starbursts or galaxies on their way to/from the starburst cloud. They make for a cosmic SFR density ${\mathrm{log}}_{10}({\rho }_{{\mathrm{SFR}}_{{\rm{H}}\alpha }}/({M}_{\odot }\,{\mathrm{yr}}^{-1}\,{\mathrm{Mpc}}^{-3}))\simeq -2.35$, which is about a quarter of the total value (${\mathrm{log}}_{10}({\rho }_{{\mathrm{SFR}}_{\mathrm{tot}}}/({M}_{\odot }\,{\mathrm{yr}}^{-1}\,{\mathrm{Mpc}}^{-3}))\simeq -1.76$) at z ≃ 7–8. Therefore, the strong Hα emitters likely had a significant role in reionization.

Citation

Rinaldi, P., Caputi, K. I., Costantin, L., Gillman, S., Iani, E., Pérez-González, P. G., …Kokorev, V. (2023). MIDIS: Strong (Hβ+[O iii]) and Hα Emitters at Redshift z ≃ 7–8 Unveiled with JWST NIRCam and MIRI Imaging in the Hubble eXtreme Deep Field. Astrophysical Journal, 952(2), Article 143. https://doi.org/10.3847/1538-4357/acdc27

• Journal Article Type: Article
• Acceptance Date: Jun 1, 2023
• Online Publication Date: Jul 25, 2023
• Publication Date: Aug 1, 2023
• Deposit Date: Oct 25, 2023
• Publicly Available Date: Oct 25, 2023
• Journal: The Astrophysical Journal
• Print ISSN: 0004-637X
• Electronic ISSN: 1538-4357
• Publisher: American Astronomical Society
• Peer Reviewed: Peer Reviewed
• Volume: 952
• Issue: 2
• Article Number: 143
• DOI: https://doi.org/10.3847/1538-4357/acdc27
• Keywords: Space and Planetary Science; Astronomy and Astrophysics
• Public URL: https://durham-repository.worktribe.com/output/1817609