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arXiv · 2203.00018

Spectroscopic confirmation of a gravitationally lensed Lyman break galaxy at z$_{[CII]}$ = 6.827 using NOEMA

S. J. Molyneux·R. Smit·D. Schaerer·R. J. Bouwens·L. Bradley·J. A. Hodge·S. N. Longmore·S. Schouws·P. van der Werf·A. Zitrin·S. Phillips
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Abstract

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] at a redshift of z = 6.8269 +/- 0.0004. This source was selected behind the strong lensing cluster Abell 1703, with an intrinsic L$_{UV}$ ~ L$^*$$_{z=7}$ luminosity and a very blue Spitzer/IRAC [3.6]-[4.5] colour, implying high equivalent width line emission of [O III]+H$\beta$. [C II] is reliably detected at 6.1$\sigma$ 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 across the source which possibly indicates rotation or an ongoing merger. We furthermore present spectral scans with no detected [C II] above 4.6$\sigma$ 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.

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S. J. Molyneux, R. Smit, D. Schaerer, R. J. Bouwens, L. Bradley, J. A. Hodge, S. N. Longmore, S. Schouws, P. van der Werf, A. Zitrin, S. Phillips. 2022-02-28. Spectroscopic confirmation of a gravitationally lensed Lyman break galaxy at z$_{[CII]}$ = 6.827 using NOEMA. https://doi.org/10.1093/mnras%2Fstac557

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