A Pilot Survey for C III] Emission in the Reionization Era: Gravitationally Lensed z ~ 7–8 Galaxies in the Frontier Fields Cluster Abell 2744
Abstract
We report results of a search for C iii] λλ1907, 1909 Å emission using Keck's MOSFIRE spectrograph in a sample of 7 z_(phot) ~ 7-8 candidates H ~ 27) lensed by the Hubble Frontier Field cluster Abell 2744. Earlier work has suggested the promise of using the C iii] doublet for redshift confirmation of galaxies in the reionization era given that Lyα (λ1216 Å) is likely attenuated by the neutral intergalactic medium. The primary challenge of this approach is the feasibility of locating C iii] emission without advanced knowledge of the spectroscopic redshift. With an integration time of 5 hr in the H band, we reach a 5σ median flux limit (in between the skylines) of 1.5 x 10^(-18) ergs cm^(−2) s^(−1) but no convincing C iii] emission was found. We also incorporate preliminary measurements from two other CLASH/HFF clusters in which, similarly, no line was detected, but these were observed to lesser depth. Using the known distribution of OH emission and the photometric redshift likelihood distribution of each lensed candidate, we present statistical upper limits on the mean total C iii] rest-frame equivalent width (EW) for our z ≃ 7-8 sample. For a signal-to-noise ratio of 5, we estimate that the typical C iii] doublet rest-frame EW is, with 95% confidence, <26 ± 5 Å. Although consistent with the strength of earlier detections in brighter objects at z ≃ 6-7, our study illustrates the necessity of studying more luminous or strongly lensed examples prior to the launch of the James Webb Space Telescope.
Additional Information
© 2015 American Astronomical Society. Received 2015 March 25; accepted 2015 April 28; published 2015 May 15. We thank the reviewer of this work for important comments. A.Z. is grateful for data products generated by Dan Coe and the CLASH team (PI: M. Postman), and for data supplied to us by Wei Zheng, Alberto Molino and group (HST grant AR 13279; PI: W. Zheng). A.Z. thanks Carrie Bridge and Adam Miller for helpful discussions, and Chuck Steidel for sharing his nominal calibration files. Support for this work was provided by NASA through Hubble Fellowship grant #HST-HF2-51334.001 A awarded by STScI, which is operated by the Association of Universities for Research in Astronomy, Inc. under NASA contract NAS 5-26555. This work is in part based on previous observations made with the NASA/ESA Hubble Space Telescope. The data presented herein were obtained at the W. M. Keck Observatory. The authors wish to recognize and acknowledge the very significant cultural role and reverence that the summit of Mauna Kea has always had within the indigenous Hawaiian community. We are most fortunate to have the opportunity to conduct observations from this mountain.Attached Files
Published - 2041-8205_805_1_L7.pdf
Submitted - 1504.07686v1.pdf
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Additional details
- Eprint ID
- 58206
- Resolver ID
- CaltechAUTHORS:20150612-083024681
- HST-HF2-51334.001-A
- NASA Hubble Fellowship
- NAS 5-26555
- NASA
- Created
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2015-06-12Created from EPrint's datestamp field
- Updated
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2021-11-10Created from EPrint's last_modified field