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

Tom J.L.C. Bakx, Yoichi Tamura, Takuya Hashimoto, Akio K. Inoue, Minju M. Lee, Ken Mawatari, Kazuaki Ota, Hideki Umehata, Erik Zackrisson, Bunyo Hatsukade, Kotaro Kohno, Yuichi Matsuda, Hiroshi Matsuo, Takashi Okamoto, Takatoshi Shibuya, Ikkoh Shimizu, Yoshiaki Taniguchi, Naoki Yoshida

Research output: Contribution to journalArticlepeer-review

Abstract

We report on the detection of the [C ii] 157.7 µm 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 [O iii] 88 µm (from previous campaigns) to [C ii] is 9.3 ± 2.6, indicative of hard interstellar radiation fields and/or a low covering fraction of photo-dissociation regions. The emission of [C ii] is cospatial to the 850 µm dust emission (90 µm rest-frame, from previous campaigns), however the peak [C ii] emission does not agree with the peak [O iii] emission, suggesting that the lines originate from different conditions in the interstellar medium. We fail to detect continuum emission at 1.5 mm (160 µm rest-frame) down to 18 µJy (3σ). This non-detection places a strong limits on the dust-spectrum, considering the 137 ± 26 µJy continuum emission at 850 µm. This suggests an unusually warm dust component (T > 80 K, 90% confidence limit), and/or a steep dust-emissivity index (βdust > 2), compared to galaxy-wide dust emission found at lower redshifts (typically T ∼ 30 − 50 K, βdust ∼ 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.

Original languageEnglish
JournalUnknown Journal
Publication statusPublished - 2020 Jan 8

Keywords

  • Galaxies: formation
  • Galaxies: high-redshift
  • Galaxies: ISM

ASJC Scopus subject areas

  • General

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