학술논문
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)
Document Type
Working Paper
Author
Rinaldi, P.; Caputi, K. I.; Costantin, L.; Gillman, S.; Iani, E.; Gonzalez, P. G. Perez; 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.; Fevre, O. Le; 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.; van Dishoeck, E.; Guedel, M.; Henning, Th.; Lagage, P. -O.; Ray, T.; Vandenbussche, B.; Waelkens, C.; Navarro-Carrera, R.; Kokorev, V.
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Subject
Language
Abstract
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]) $\simeq 87 - 2100$ {\AA}. 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$\alpha$) $\simeq 200-3000$ {\AA}. 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.
Comment: 18 pages, 11 figures. The paper has been accepted for publication in ApJ
Comment: 18 pages, 11 figures. The paper has been accepted for publication in ApJ