I report a tentative (∼4σ) emission line at ν=100.84GHz from "COS-3mm-1'", a 3mm-selected galaxy reported by Williams et al. 2019 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 3mm-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.
@article{arxiv.2102.07772,
title = {A tentative emission line at z=5.8 from a 3mm-selected galaxy},
author = {Jorge A. Zavala},
journal= {arXiv preprint arXiv:2102.07772},
year = {2021}
}