S20B0002abst
S20B0002
This is a resubmission of our approved proposals of S19B-052N, whose FOCAS observations were not conducted due to bad weather. We propose deep Subaru/FOCAS follow-up for two extreme [Oiii] emitters at zspec=0.828 and 0.728 whose [Oiii]5007 equivalent widths (EWs) are ∼5000 Å, highest among objects reported to date. These emitters are identified in our unique ∼650 deg2 Subaru/Hyper-Suprime Cam Survey. The EWs of these two emitters can not be reproduced by classical stellar population synthesis models, and hard ionizing spectra (such as produced by massive star binary population) are needed. [Nii]/Hα and [Sii]/Hα ratios obtained in our Keck/MOSFIRE spectroscopy locate the two emitters in the “star-forming" regions in the BPT diagrams. With the FOCAS spectra, we will 1) determine metallicities using the [Oiii]4363 line and 2) measure the hardness of the ionizing spectra with the Heii4686/Hβ line ratio. We will discuss whether the new binary population model can explain the properties of these two extreme [Oiii] emitters, or modification of our knowledge of the stellar population model is needed. This program is important verification of the current stellar population models, and crucial for understanding cosmic reionization sources.
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