I report a tentative (∼4σ) emission line at ν = 100.84 GHz from “COS-3mm-1,” a 3 mm selected galaxy reported by Williams et al. that is undetected at optical and near-infrared wavelengths. The line was found in the ALMA Science Archive after re-processing ALMA band 3 observations targeting a different source. Assuming the line corresponds to the CO(6 → 5) transition, this tentative detection implies a spectroscopic redshift of z = 5.857, in agreement with the galaxy’s redshift constraints from multi-wavelength photometry. This would make this object the highest redshift 3 mm selected galaxy and one of the highest redshift dusty star-forming galaxies known to-date. Here, I report the characteristics of this tentative detection and the physical properties that can be inferred assuming the line is real. Finally, I advocate for follow-up observations to corroborate this identification and to confirm the high-redshift nature of this optically-dark dusty star-forming galaxy.

我在ν  = 100.84 GHz 处报告了一条来自 Williams 等人报告的 3 mm 选定星系“COS-3mm-1”的暂定 (∼4 σ ) 发射线。在光学和近红外波长处无法检测到。在重新处理针对不同来源的 ALMA 波段 3 观测后，在 ALMA 科学档案中发现了这条线。假设这条线对应于 CO(6 → 5) 跃迁，这种初步检测意味着z的光谱红移 = 5.857，与多波长光度法的星系红移约束一致。这将使该天体成为最高红移 3 毫米的选定星系，也是迄今为止已知的最高红移尘埃恒星形成星系之一。在这里，我报告了这种试探性检测的特征以及假设这条线是真实的可以推断出的物理特性。最后，我主张进行后续观察，以证实这一识别并确认这个光学暗尘埃恒星形成星系的高红移性质。