We report a ground-based detection of the [OI] 63-um line in a z=6.027 gravitationally lensed dusty star-forming galaxy (DSFG) G09.83808 using the APEX SEPIA 660 receiver, the first unambiguous detection of the [OI]63 line beyond redshift 3, and the first obtained from the ground. The [OI]63 line is robustly detected at 22±5 Jy km s−1, corresponding to an intrinsic (de-lensed) luminosity of (5.4±1.3)×109 L⊙. With the [OI]63/[CII] luminosity ratio of 4, the [OI]63 line is the main coolant of the neutral gas in this galaxy, in agreement with model predictions. The high [OI]63 luminosity compensates for the pronounced [CII] deficit ([CII]/FIR≃4×10−4). Using photon-dominated region models, we derive a source-averaged gas density n=104.0 cm−3, and far-UV field strength G=104G0, comparable to the z=2-4 DSFG population. If G09.83808 represents a typical high-redshift DSFG, the [OI]63 line from z=6 non-lensed DSFGs should be routinely detectable in ALMA Band 9 observations with ∼15 min on-source, opening a new window to study the properties of the earliest DSFGs.
@article{arxiv.1912.07652,
title = {First detection of the [OI] 63-um emission from a redshift 6 dusty galaxy},
author = {M. Rybak and J. A. Zavala and J. A. Hodge and C. M. Casey and P. van der Werf},
journal= {arXiv preprint arXiv:1912.07652},
year = {2020}
}