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

ABSTRACT We present results of dust continuum and C ii\, 158\, 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 ₑ₄ₒₓ=160\, m continuum 1\, sensitivity of 13. 0\, Jy \, beam^ -1 and a C ii emission line 1\, 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\, m line emission are detected at the expected frequency of νC ii= 163. 791\, GHz and the sky location of GN-z11. The upper limits show that GN-z11 is neither luminous in LIR nor LC ii, with a dust mass 3\, limit of log\, (M ₃ₔₒₓ/ { M }) \, \, 6. 5-6. 9 and with a C ii based molecular gas mass 3\, 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.