Probing infrared eXcess to investigate early-Universe dust (PIXIEDust)

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 1σ depth of 2.0, 2.0, and 1.5 μJy at rest-frame 158, 88 μm, and across all the data, respectively. This constrains average dust masses to be below < 105 M at 3σ and dust-to-stellar mass ratios to be below 3.7 × 10−4 (assuming Tdust = 50 K and βdust = 2.0). Binning by redshift (8 < z < 9.5 and 9.5 < z < 15), UV-continuum slope (βUV ≶ −2), and stellar mass (log10 M∗/M ≶ 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.