Recent observations have suggested that the CIII]λ1907/1909 emission lines could be alternative diagnostic lines for galaxies in the reionization epoch. We use the F128N narrowband filter on the Hubble Space Telescope's (HST) Wide Field Camera 3 (WFC3) to search for CIII] emission in a sample of five galaxies at z = 5.7 in the Subaru Deep Field and the Subaru/XMM-Newton Deep Field. Using the F128N narrowband imaging, together with the broadband imaging, we do not detect CIII] emission for the five galaxies with JAB ranging from 24.10 -- 27.00 in our sample. For the brightest galaxy J132416.13+274411.6 in our sample (z = 5.70, JAB=24.10), which has a significantly higher signal to noise, we report a CIII] flux of 3.34±1.81×10−18ergs−1cm−2, which places a stringent 3-σ upper limit of 5.43×10−18ergs−1cm−2 on CIII] flux and 6.57 \AA\ on the CIII] equivalent width. Using the stacked image, we put a 3-σ upper limit on the mean CIII] flux of 2.55×10−18ergs−1cm−2, and a 3-σ upper limit on the mean CIII] equivalent width of 4.20 {\AA} for this sample of galaxies at z = 5.70. Combined with strong CIII] detection reported among high-z galaxies in the literature, our observations suggest that the equivalent widths of CIII] from galaxies at z > 5.70 exhibit a wide range of distribution. Our strong limits on CIII] emission could be used as a guide for future observations in the reionization epoch.
@article{arxiv.1612.00902,
title = {Constraining C iii] Emission in a Sample of Five Luminous z = 5.7 Galaxies},
author = {Jiani Ding and Zheng Cai and Xiaohui Fan and Daniel P. Stark and Fuyan Bian and Linhua Jiang and Ian D. McGreer and Brant E. Robertson and Brian Siana},
journal= {arXiv preprint arXiv:1612.00902},
year = {2017}
}