The NOEMA observations of GN-z11: constraining the neutral interstellar medium and dust formation in the heart of cosmic reionization at z = 10.6

We present results of dust continuum and [C ii]\, 158\, μ m emission line observations of a remarkably UV luminous (MUV = −21.6) galaxy at z = 10.603: GN-z11. Using the Northern Extended Millimeter Array (NOEMA), observations have been carried out over multiple observing cycles. We achieved a high sensitivity resulting in a λ ᵣₑₛₜ=160\, μ m continuum 1\, σ sensitivity of 13.0\, μ Jy \, beam⁻¹ and a [C ii] emission line 1\, σ sensitivity of 31\, mJy\, beam⁻¹\, km \, s⁻¹ using 50\, km \, s⁻¹ binning with a ~ 2\, arcsec synthesized beam. Neither dust continuum nor [C ii]\, 158\, μ m line emission are detected at the expected frequency of ν[C ii]= 163.791\, GHz and the sky location of GN-z11. The upper limits show that GN-z11 is neither luminous in LIR nor L[C ii], with a dust mass 3\, σ limit of log\, (Mdust/ M) \, <\, 6.5-6.9 and with a [C ii] based molecular gas mass 3\, σ limit of log (Mmol, [C ii]/ M) \, < \, 9.3. Together with radiative transfer calculations, we also investigated the possible cause of the dust poor nature of the GN-z11 showed by the blue colour in the UV continuum of GN-z11 (βUV = −2.4), and found that ≳3 × deeper observations are crucial to study dust production at very high-redshift. Nevertheless, our observations show the crucial role of deep mm/submm observations of very high-redshift galaxies to constrain multiple phases in the interstellar medium.