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Spectroscopic confirmation of a gravitationally lensed Lyman break galaxy at z[C II]= 6.827 using NOEMA

Molyneux, SJ, Smit, R, Schaerer, D, Bouwens, RJ, Bradley, L, Hodge, JA, Longmore, SN, Schouws, S, van der Werf, P, Zitrin, A and Phillips, S (2022) Spectroscopic confirmation of a gravitationally lensed Lyman break galaxy at z[C II]= 6.827 using NOEMA. Monthly Notices of the Royal Astronomical Society, 512 (1). pp. 535-543. ISSN 0035-8711

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We present the spectroscopic confirmation of the brightest known gravitationally lensed Lyman break galaxy in the Epoch of Reionisation, A1703-zD1, through the detection of [C II]158 μm at a redshift of z = 6.8269 ± 0.0004. This source was selected behind the strong lensing cluster Abell 1703, with an intrinsic LUV∼L∗z=7 luminosity and a very blue Spitzer/IRAC [3.6]–[4.5] colour, implying high equivalent width line emission of [O III]+Hβ. [C II] is reliably detected at 6.1σ co-spatial with the rest-frame UV counterpart, showing similar spatial extent. Correcting for the lensing magnification, the [C II] luminosity in A1703-zD1 is broadly consistent with the local L[CII] – SFR relation. We find a clear velocity gradient of 103 ± 22 km s−1 across the source which possibly indicates rotation or an ongoing merger. We furthermore present spectral scans with no detected [C II] above 4.6σ in two unlensed Lyman break galaxies in the EGS-CANDELS field at z ∼ 6.6–6.9. This is the first time that NOEMA has been successfully used to observe [C II] in a ‘normal’ star-forming galaxy at z > 6, and our results demonstrate its capability to complement ALMA in confirming galaxies in the Epoch of Reionisation.

Item Type: Article
Additional Information: This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society ©: 2022 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.
Uncontrolled Keywords: 0201 Astronomical and Space Sciences
Subjects: Q Science > QB Astronomy
Q Science > QC Physics
Divisions: Astrophysics Research Institute
Publisher: Oxford University Press (OUP)
Date Deposited: 08 Mar 2022 15:06
Last Modified: 28 Mar 2022 15:00
DOI or ID number: 10.1093/mnras/stac557
URI: https://researchonline.ljmu.ac.uk/id/eprint/16467
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