SILVERRUSH. III. Deep optical and near-infrared spectroscopy for Lyα and UV-nebular lines of bright Lyα emitters at z = 6-7
- Shibuya, T;
- Ouchi, M;
- Harikane, Y;
- Rauch, M;
- Ono, Y;
- Mukae, S;
- Higuchi, R;
- Kojima, T;
- Yuma, S;
- Lee, CH;
- Furusawa, H;
- Konno, A;
- Martin, CL;
- Shimasaku, K;
- Taniguchi, Y;
- Kobayashi, MAR;
- Kajisawa, M;
- Nagao, T;
- Goto, T;
- Kashikawa, N;
- Komiyama, Y;
- Kusakabe, H;
- Momose, R;
- Nakajima, K;
- Tanaka, M;
- Wang, SY
- et al.
Published Web Location
http://arxiv.org/pdf/1705.00733.pdfAbstract
We present Lyα and UV-nebular emission line properties of bright Lyα emitters (LAEs) at z = 6-7 with a luminosity of log LLyα/[erg s-1] = 43-44 identified in the 21 deg2 area of the SILVERRUSH early sample developed with the Subaru Hyper Suprime-Cam survey data. Our optical spectroscopy newly confirms 21 bright LAEs with clear Lyα emission, and contributes to making a spectroscopic sample of 96 LAEs at z = 6-7 in SILVERRUSH. From the spectroscopic sample, we select seven remarkable LAEs as bright as Himiko and CR7 objects, and perform deep Keck/MOSFIRE and Subaru/nuMOIRCS near-infrared spectroscopy reaching the 3 σ flux limit of ∼2 × 10-18 erg s-1 for the UV-nebular emission lines of He II λ1640, CIV λλ1548,1550, and OIII]λλ1661,1666. Except for one tentative detection of C IV, we find no strong UV-nebular lines down to the flux limit, placing the upper limits of the rest-frame equivalent widths (EW0) of ∼2-4 A for CIV, He II, and OIII] lines. We also investigate the VLT/X-SHOOTER spectrum of CR7 whose 6 σ detection of He II is claimed by Sobral et al. Although two individuals and the ESO archive service carefully reanalyzed the X-SHOOTER data that are used in the study of Sobral et al., no He II signal of CR7 is detected, supportive of weak UV-nebular lines of the bright LAEs even for CR7. The spectral properties of these bright LAEs are thus clearly different from those of faint dropouts at z ∼ 7 that have strong UV-nebular lines shown in the various studies. Comparing these bright LAEs and the faint dropouts, we find anti-correlations between the UV-nebular line EW0 and the UV-continuum luminosity, which are similar to those found at z ∼ 2-3.
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