Updated Measurements of [O iii] 88 μm, [C ii] 158 μm, and Dust Continuum Emission from a z = 7.2 Galaxy

Abstract

We present updated measurements of the [O iii] 88 μm, [C ii] 158 μm, and dust continuum emission from a star-forming galaxy at z = 7.212, SXDF-NB1006-2, by utilizing Atacama Large Millimeter/submillimeter Array (ALMA) archival data sets analysed in previous studies and data sets that have not been analysed before. The follow-up ALMA observations with higher angular resolution and sensitivity reveal a clumpy structure of the [O iii] emission on a scale of 0.32–0.85 kpc. We also combined all the ALMA [O iii] ([C ii]) data sets and updated the [O iii] ([C ii]) detection to 5.9σ (3.6σ–4.5σ). The non-detection of [C ii] with data from the REBELS large program implies the incompleteness of spectral-scan surveys using [C ii] to detect galaxies with high star formation rates (SFRs) but marginal [C ii] emission at high-z. The dust continuum at 90 and 160 μm remains undetected, indicating little dust content of <3.9 × 106 M ⊙ (3σ), and we obtained a more stringent constraint on the total infrared luminosity. We updated the [O iii]/[C ii] luminosity ratios to 10.2 ± 4.7 (6.1 ± 3.5) and 20 ± 12 (9.6 ± 6.1) for the 4.5σ and 3.6σ [C ii] detections, respectively, where the ratios in the parentheses are corrected for the surface brightness dimming effect on the extended [C ii] emission. We also found a strong [C ii] deficit (0.6–1.3 dex) between SXDF-NB1006-2 and the mean L [C II]−SFR relation of galaxies at 0 < z < 9.