Detection of the Far-infrared [O III] and Dust Emission in a Galaxy at Redshift 8.312: Early Metal Enrichment in the Heart of the Reionization Era
Shibuya, Takatoshi; Inoue, Akio K.; Hashimoto, Takuya; Tamura, Yoichi; Kohno, Kotaro; Hatsukade, Bunyo; Zackrisson, Erik; Mawatari, Ken; Takeuchi, Tsutomu T.; Christensen, Lise; Matsuo, Hiroshi; Umehata, Hideki; Taniguchi, Yoshiaki; Lee, Minju M.; Ota, Kazuaki; Matsuda, Yuichi; Okamoto, Takashi; Shimizu, Ikkoh; Yoshida, Naoki; Binggeli, Christian; Asano, Ryosuke S.; Sunaga, Kaho
Japan, Sweden, Denmark, United Kingdom
Abstract
We present the Atacama Large Millimeter/submillimeter Array detection of the [O III] 88 μm line and rest-frame 90 μm dust continuum emission in a Y-dropout Lyman break galaxy (LBG), MACS0416_Y1 lying behind the Frontier Field cluster MACS J0416.1-2403. This [O III] detection confirms the LBG with a spectroscopic redshift of z = 8.3118 ± 0.0003, making this object one of the farthest galaxies ever identified spectroscopically. The observed 850 μm flux density of 137 ± 26 μJy corresponds to a de-lensed total infrared (IR) luminosity of {L}IR}=(1.7+/- 0.3)× {10}11 {L}⊙ if assuming a dust temperature of T dust = 50 K and an emissivity index of β = 1.5, yielding a large dust mass of 4× {10}6{M}⊙ . The ultraviolet-to-far-IR spectral energy distribution modeling where the [O III] emissivity model is incorporated suggests the presence of a young (τ age ≈ 4 Myr), star-forming ({SFR}≈ 60 {M}⊙ yr-1), moderately metal-polluted (Z ≈ 0.2Z ⊙) stellar component with a mass of M star = 3 × 108 M ⊙. An analytic dust mass evolution model with a single episode of star formation does not reproduce the metallicity and dust mass in τ age ≈ 4 Myr, suggesting a pre-existing evolved stellar component with M star ∼ 3 × 109 M ⊙ and τ age ∼ 0.3 Gyr as the origin of the dust mass.