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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.

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 Thumbnail


P. Rinaldi

K. I. Caputi

L. Costantin

S. Gillman

E. Iani

P. G. Pérez-González

G. Östlin

L. Colina

T. R. Greve

H. U. Noorgard-Nielsen

G. S. Wright

A. Alonso-Herrero

J. Álvarez-Márquez

A. Eckart

M. García-Marín

J. Hjorth

O. Ilbert

S. Kendrew

A. Labiano

O. Le Fèvre

J. Pye

T. Tikkanen

F. Walter

P. van der Werf

M. Annunziatella

R. Azzollini

A. Bik

L. Boogaard

S. E. I. Bosman

A. Crespo Gómez

I. Jermann

D. Langeroodi

J. Melinder

R. A. Meyer

T. Moutard

F. Peissker

M. Topinka

E. van Dishoeck

M. Güdel

Th. Henning

P.-O. Lagage

T. Ray

B. Vandenbussche

C. Waelkens

R. Navarro-Carrera

V. Kokorev


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.


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.

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
Keywords Space and Planetary Science; Astronomy and Astrophysics
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Copyright Statement
© 2023. The Author(s). Published by the American Astronomical Society.
Original content from this work may be used under the terms of the Creative Commons Attribution 4.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.

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