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Abstract We present an analysis of rest-frame UV continuum slopes, β, using a sample of 1011 galaxies at 6. 5 178. 9 arcmin 2 of unmasked blank sky. We correct our UV slopes for the photometric error coupling bias using 200, 000 power-law spectral energy distributions for each β = −1, −1. 5, −2, −2. 5, −3 in each field, finding biases as large as Δ β ≃ −0. 55 for the lowest signal-to-noise ratio galaxies in our sample. Additionally, we simulate the impact of rest-UV line emission (including Ly α) and damped Ly α systems on our measured β, finding biases as large as 0. 5–0. 6 for the most extreme systems. We find a decreasing trend with redshift of β = −1. 51 ± 0. 08 − (0. 097 ± 0. 010) × z, with potential evidence for Population III stars or top-heavy initial mass functions in a subsample of 68 β + σ β d β / d log 10 (M ⋆ / M ⊙) from 0. 22 ± 0. 02 at z ≃ 7 to 0. 81 ± 0. 13 at z ≃ 11. 5 implies that dust produced in core-collapse supernovae at early times may be ejected via outflows from low-mass galaxies. We also observe a flatter d β / d M UV = 0. 03 ± 0. 02 at z ≃ 7 and a shallower d β / d log 10 (M ⋆ / M ⊙) at z < 11 than seen by the Hubble Space Telescope, unveiling a new population of low-mass, faint galaxies reddened by dust produced in the stellar winds of asymptotic giant branch stars or carbon-rich Wolf–Rayet binaries.
Austin et al. (Wed,) studied this question.