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] 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 continuum sensitivity of and a [C ii] emission line sensitivity of using binning with a synthesized beam. Neither dust continuum nor [C ii] line emission are detected at the expected frequency of ν[C ii] 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 limit of and with a [C ii] based molecular gas mass limit of log (Mmol, [C ii]. 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.