Tom J. L. C. Bakx, Hiddo Algera, Jean-Baptiste Jolly, Clarke J. Esmerian, K. K. Knudsen, Laura Sommovigo, Joris Witstok, Stefano Carniani, Jianhang Chen, Stephen Eales, A. Ferrara, Yoshinobu Fudamoto, Masato Hagimoto, Takuya Hashimoto, Hanae Inami, Akio Inoue, T. Khouri, Ikki Mitsuhashi, Gunnar Nyman, Gustav Olander, S. Serjeant, Renske Smit, Ilsang Yoon, Jorge A. Zavala, S. Aalto, Caitlin M. Casey, Yoichi Tamura, W. H. T. Vlemmings
ABSTRACT Despite the implied presence of dust through reddened UV emission in high-redshift galaxies, no dust emission has been detected in the (sub)millimetre regime beyond $z > 8.3$. This study combines around 200 h of Atacama Large Millimetre/submillimetre Array (ALMA) and Northern Extended Millimetre Array (NOEMA) observations on 10 $z > 8$ galaxies, revealing no significant dust emission down to a $1 \sigma$ depth of 2.0, 2.0, and $1.5 \, \mu$Jy at rest-frame 158, 88 $\mu$m, and across all the data, respectively. This constrains average dust masses to be below $< 10^{5}$ M$_{\odot }$ at $3 \sigma$ and dust-to-stellar mass ratios to be below $3.7 \times {} 10^{-4}$ (assuming $T_{\rm dust} = 50$ K and $\beta _{\rm dust} = 2.0$). Binning by redshift ($8 < z < 9.5$ and $9.5 < z < 15$), UV-continuum slope ($\beta _{\rm UV} \lessgtr -2$), and stellar mass ($\log _{10} M_{\ast }/{\rm {M}_{\odot }} \lessgtr 9$) yields similarly stringent constraints. Combined with other studies, these results are consistent with inefficient dust build-up in the $z > 8$ Universe, likely due to inefficient supernova production, limited interstellar grain growth and/or ejection by outflows. We provide data and tools online to facilitate community-wide high-redshift dust searches.