MIDIS: The Relation between Strong (Hβ + [O III]) Emission, Star Formation, and Burstiness around the Epoch of Reionization
Nørgaard-Nielsen, H. U.; Östlin, G.; Güdel, M.; Ray, T. P.; Colina, L.; Greve, T. R.; Walter, F.; Henning, Th.; van der Werf, P.; Le Fèvre, O.; Lagage, P. O.; Melinder, J.; Caputi, K. I.; Hjorth, J.; Iani, E.; Pérez-González, P. G.; Rinaldi, P.; Eckart, A.; Labiano, A.; Wright, G. S.; Crespo Gómez, A.; Álvarez-Márquez, J.; Boogaard, L.; Peissker, F.; Costantin, L.; Gillman, S.; Jermann, I.; Langeroodi, D.
Netherlands, Denmark, Spain, Sweden, United Kingdom, Germany, France, Austria, Switzerland, Ireland
Abstract
We investigate the properties of strong (Hβ + [O III]) emitters before and after the end of the "Epoch of Reionization" from z = 8 to z = 5.5. We make use of ultradeep JWST/NIRCam imaging in the parallel field (P2) of the MIRI Deep Imaging Survey (MIDIS) in the Hubble eXtreme Deep Field (H-XDF), in order to select prominent (Hβ + [O III]) emitters (with rest-frame equivalent width (EW0) ≳ 100 Å) at z = 5.5–7, based on their flux density enhancement in the F356W band with respect to the spectral energy distribution continuum. We complement our selection with other (Hβ + [O III]) emitters from the literature at similar and higher (z = 7‑8) redshifts. We find (nonindependent) anticorrelations between EW0(Hβ + [O III]) and both galaxy stellar mass and age, in agreement with previous studies, and a positive correlation with specific star formation rate (sSFR). On the SFR–M ⋆ plane, the (Hβ + [O III]) emitters populate both the star formation main sequence and the starburst region, which become indistinguishable at low stellar masses (