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Abstract We present new ALMA observations and physical properties of a Lyman break galaxy at z = 7. 15. Our target, B14-65666, has a bright ultra-violet (UV) absolute magnitude, MUV ≈ −22. 4, and has been spectroscopically identified in Lyα with a small rest-frame equivalent width of ≈4 Å. A previous Hubble Space TElescope (HST) image has shown that the target is composed of two spatially separated clumps in the rest-frame UV. With ALMA, we have newly detected spatially resolved O iii 88 μm, C ii 158 μm, and their underlying dust continuum emission. In the whole system of B14-65666, the O iii and C ii lines have consistent redshifts of 7. 1520 ± 0. 0003, and the O iii luminosity, (34. 4 ± 4. 1) × 108 L⊙, is about three times higher than the C ii luminosity, (11. 0 ± 1. 4) × 108 L⊙. With our two continuum flux densities, the dust temperature is constrained to be Td ≈ 50–60 K under the assumption of a dust emissivity index of βd = 2. 0–1. 5, leading to a large total infrared luminosity of LTIR ≈ 1 × 1012 L⊙. Owing to our high spatial resolution data, we show that the O iii and C ii emission can be spatially decomposed into two clumps associated with the two rest-frame UV clumps whose spectra are kinematically separated by ≈200 km s−1. We also find these two clumps have comparable UV, infrared, O iii, and C ii luminosities. Based on these results, we argue that B14-65666 is a starburst galaxy induced by a major merger. The merger interpretation is also supported by the large specific star formation rate (defined as the star formation rate per unit stellar mass), sSFR = 260^+119-₅₇\: Gyr−1, inferred from our SED fitting. Probably, a strong UV radiation field caused by intense star formation contributes to its high dust temperature and the O iii-to-C ii luminosity ratio.
Hashimoto et al. (Tue,) studied this question.