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

Abstract : We present the spectroscopic confirmation of the brightest known gravitationally lensed Lyman-break galaxy in the Epoch of Reionization (EoR), A1703-zD1, through the detection of [C II] 158 $\mu$m at a redshift of z = 6.8269 ± 0.0004. This source was selected behind the strong lensing cluster Abell 1703, with an intrinsic luminosity and a very blue Spitzer/Infrared Array Camera (IRAC) [3.6]-[4.5] colour, implying high equivalent width line emission of [O III] + Hβ. [C II] is reliably detected at 6.1σ cospatial with the rest-frame ultraviolet (UV) counterpart, showing similar spatial extent. Correcting for the lensing magnification, the [C II] luminosity in A1703-zD1 is broadly consistent with the local $L_{\rm [C\, {\small II}]}$-star formation rate (SFR) relation. We find a clear velocity gradient of 103 ± 22 km $\rm s^{-1}$ across the source that 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 Extended Groth Strip (EGS)-Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey (CANDELS) field at z ~ 6.6-6.9. This is the first time that the Northern Extended Millimeter Array (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 the Atacama Large Millimeter/submillimeter Array (ALMA) in confirming galaxies in the EoR.
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Contributor : Nathalie POTHIER Connect in order to contact the contributor
Submitted on : Thursday, May 19, 2022 - 9:15:21 AM
Last modification on : Wednesday, June 1, 2022 - 4:13:00 AM

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S. J. Molyneux, R. Smit, D. Schaerer, R. J. Bouwens, L. Bradley, et al.. Spectroscopic confirmation of a gravitationally lensed Lyman-break galaxy at z[C II] = 6.827 using NOEMA. Monthly Notices of the Royal Astronomical Society, 2022, 512, pp.535-543. ⟨10.1093/mnras/stac557⟩. ⟨insu-03672015⟩



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