\[tab:3811\], while the quoted uncertainties in the rest of the paper refer to random uncertainties.

Finally, to make sure that the error spectrum initially obtained from the pipeline does not underestimate the noise level, we scaled the error spectrum such that the standard deviation of the signal-to-noise ratio (S/N) in the sky dominated region is unity. The typical scale factor was $3.0 \pm 0.1$.

Results {#sec:results}
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Line Detection
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We visually searched for emission lines in the extracted 1D spectra as well as 2D spectra at the expected positions of our targets. We take a conservative appoach of presenting objects for which an emission line is independently detected on more than one night, minimizing the possibility of a spurious detection. In other words, we regarded it as a spurious detection if the emission was detected on only one night out of four nights. This criterion yielded only one line detection among the 30 objects originally targeted, at $\lambda_{\rm obs}= 10532.2 \pm 1.3 $ Å, and with $6.5 \sigma$ significance. The rest remained undetected ($< 3\sigma$). Figure \[fig:spec\] shows the 1D and 2D spectra of the object with emission, z7\_GSD\_3811. The emission is detected on more than one night at 