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MIDIS: Strong (Hb + [OIII]) and Ha emitters at redshift \(z \simeq 7-8\) unveiled with JWST/NIRCam and MIRI imaging in the Hubble eXtreme Deep Field (XDF)

We make use of \textit{JWST} medium and broad-band NIRCam imaging, along with ultra-deep MIRI \(5.6 \rm \mu m\) imaging, in the Hubble eXtreme Deep Field (XDF) to identify prominent line emitters at \(z\simeq 7-8\). Out of a total of 58 galaxies at \(z\simeq 7-8\), we find 18 robust candidates (\(\s...

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Published in:arXiv.org 2023-06
Main Authors: Rinaldi, P, Caputi, K I, Costantin, L, Gillman, S, Iani, E, Perez Gonzalez, P G, Oestlin, G, Colina, L, Greve, T, Noorgard-Nielsen, H U, Wright, G S, Alonso-Herrero, A, Alvarez-Marquez, J, Eckart, A, Garcia-Marin, M, Hjorth, J, Ilbert, O, Kendrew, S, Labiano, A, O Le Fevre, Pye, J, Tikkanen, T, Walter, F, van der Werf, P, Ward, M, Annunziatella, M, Azzollini, R, Bik, A, Boogard, L, Bosman, S, Crespo, A, Jermann, I, Langeroodi, D, Melinder, J, Meyer, R, Moutard, T, Peissker, F, Topinka, M, E van Dishoeck, Guedel, M, Henning, Th, P -O Lagage, Ray, T, Vandenbussche, B, Waelkens, C, Navarro-Carrera, R, Kokorev, V
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Language:English
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Summary:We make use of \textit{JWST} medium and broad-band NIRCam imaging, along with ultra-deep MIRI \(5.6 \rm \mu m\) imaging, in the Hubble eXtreme Deep Field (XDF) to identify prominent line emitters at \(z\simeq 7-8\). Out of a total of 58 galaxies at \(z\simeq 7-8\), we find 18 robust candidates (\(\simeq\)31\%) for (H\(\beta\) + [OIII]) emitters, based on their enhanced fluxes in the F430M and F444W filters, with EW\(_{0}\)(H\(\beta\) +[OIII]) \(\simeq 87 - 2100\) Å. Among these emitters, 16 lie in the MIRI coverage area and 12 exhibit a clear flux excess at \(5.6 \, \rm \mu m\), indicating the simultaneous presence of a prominent H\(\alpha\) emission line with EW\(_{0}\)(H\(\alpha\)) \(\simeq 200-3000\) Å. This is the first time that H\(\alpha\) emission can be detected in individual galaxies at \(z>7\). The H\(\alpha\) line, when present, allows us to separate the contributions of H\(\beta\) and [OIII] to the (H\(\beta\) +[OIII]) complex, and derive H\(\alpha\)-based star formation rates (SFRs). We find that in most cases [OIII]/H\(\beta > 1\). Instead, two galaxies have [OIII]/H\(\beta < 1\), indicating that the NIRCam flux excess is mainly driven by H\(\beta\). This could potentially imply extremely low metallicities. 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 \(\rm log_{10}(\rho_{SFR_{H\alpha}}) \simeq -2.35\), which is about a quarter of the total value (\(\rm log_{10}(\rho_{SFR_{tot}}) \simeq -1.76\)) at \(z\simeq 7-8\). Therefore, the strong H\(\alpha\) emitters likely had a significant role in reionization.
ISSN:2331-8422
DOI:10.48550/arxiv.2301.10717