摘要
A&A 699, A336 (2025) We investigate the coevolution of metals and dust in 173 galaxies at4.0<z<11.4using NIRSpec spectroscopy. Focusing on galaxies with extremely low dust attenuation, we explore their physical processes using a new CIGALE version that incorporates spectroscopic and photometric data. Comparing observations with models, we derive key physical parameters. We identify 49 galaxies with extremely low dust attenuation (GELDAs), characterized byA_(FUV)=0within2σandM_(star)<10⁹ M_(⊙) . The stacked spectra reveal a very blue UV slope ( β_(FUV) =-2.451±-0.066 ) and Balmer decrement H α /H β= 2.932±-0.660 , consistent with no dust attenuation. GELDAs are more common atz>8.8(83.3%) than atz<8.8(26.3%) suggesting they dominate the early Universe. Assuming a prior FIR dust spectrum (from ALPINE), we examine dust-stellar mass trends. TheM_(dust)vs.M_(star)diagram shows upper and lower sequences linked by possible transitional galaxies. A transition atM_(star)=10⁸.5 M_(⊙)( Z_(crit)=12+\log{₁₀}{(}{O}/H)=7.60orZ/Z_(⊙)=0.1 ) may mark the shift from stellar dust production to ISM grain growth, in agreement with theoretical predictions. Our full sample has a high mean gas fraction ( f_(gas)>0.9 ), indicating retained gas across all galaxies. Their small sizes and large gas masses imply high gas surface densities but relatively low star formation efficiency. High-redshift GELDAs may naturally explain the observed excess of bright galaxies atz>9compared to theoretical expectations.