paper

ALMA uncovers the [CII] emission and warm dust continuum in a z = 8.31 Lyman break galaxy

arXiv:2001.02812 · doi:10.1093/mnras/staa509

Abstract

We report on the detection of the [CII] 157.7 m emission from the Lyman break galaxy (LBG) MACS0416_Y1 at z = 8.3113, by using the Atacama Large Millimeter/submillimeter Array (ALMA). The luminosity ratio of [OIII] 88 m (from previous campaigns) to [CII] is 9.31 2.6, indicative of hard interstellar radiation fields and/or a low covering fraction of photo-dissociation regions. The emission of [CII] is cospatial to the 850 m dust emission (90 m rest-frame, from previous campaigns), however the peak [CII] emission does not agree with the peak [OIII] emission, suggesting that the lines originate from different conditions in the interstellar medium. We fail to detect continuum emission at 1.5 mm (160 m rest-frame) down to 18 Jy (3). This nondetection places a strong limit on the dust spectrum, considering the 137 26 Jy continuum emission at 850 m. This suggests an unusually warm dust component (T 80 K, 90% confidence limit), and/or a steep dust-emissivity index ( 2), compared to galaxy-wide dust emission found at lower redshifts (typically T 30 - 50 K, 1 - 2). If such temperatures are common, this would reduce the required dust mass and relax the dust production problem at the highest redshifts. We therefore warn against the use of only single-wavelength information to derive physical properties, recommend a more thorough examination of dust temperatures in the early Universe, and stress the need for instrumentation that probes the peak of warm dust in the Epoch of Reionization.

arXiv comment15 pages, 8 figures, Accepted by MNRAS

References in corpus (96)

Cited by in corpus (90)