NOEMA observations of GN-z11: Constraining Neutral Interstellar Medium and Dust Formation in the Heart of Cosmic Reionization at $z=10.6$

Abstract

We present results of dust continuum and [CII]$158\hat{\mathrm{I}}¼\mathrm{m}$ emission line observations of a remarkably UV-luminous ($M_{\mathrm{UV}}=-21.6$) 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 $\hat{I}{»}_{\mathrm{rest}}=160\hat{\mathrm{I}}¼\mathrm{m}$ continuum $1\ddot{I}ƒ$ depth of $13.0\hat{\mathrm{I}}¼Jy/beam$ and a [CII] emission line $1\ddot{I}ƒ$ sensitivity of $31mJy/beamkm/s$ using $50km/s$ binning with a $\sim 2\mathrm{arcsec}$ synthesized beam. Neither dust continuum nor [CII]$158\hat{\mathrm{I}}¼\mathrm{m}$ line emission are detected at the expected frequency of $\hat{I}{½}_{[\mathrm{CII}]}=163.791\mathrm{GHz}$ and the sky location of GN-z11. The upper limits show that GN-z11 is neither luminous in $L_{\mathrm{IR}}$ nor $L_{[\mathrm{CII}]}$, with a dust mass $3\ddot{I}ƒ$ limit of $\log (M_{\mathrm{dust}}/{\mathrm{M}}_{\odot })<6.5-6.9$ and with a [CII] based molecular gas mass $3\ddot{I}ƒ$ limit of $\log (M_{\mathrm{mol},[\mathrm{CII}]}/{\mathrm{M}}_{\odot })<9.3$. Together with radiative transfer calculations, we also investigated the possible cause of the dust poor nature of the GN-z11 showed by the blue color in the UV continuum of GN-z11 (${\hat{I}}_{\mathrm{UV}}^2=-2.4$), and found that $\gtrsim 3\times$ 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.

submitted to MNRAS, 7 pages, 4 figures, 1 table