Faint [C i](1-0) emission in z ∼ 3.5 radio galaxies

We present Atacama Large Millimeter/sub-millimeter Array neutral carbon, [CI](1-0), line observations that probe molecular hydrogen gas (H-2) within seven radio galaxies at z = 2.9-4.5 surrounded by extended (greater than or similar to 100 kpc) Ly alpha nebulae. We extract [CI](1-0) emission from the radio-active galactic nuclei (AGNs) host galaxies whose positions are set by near-infrared detections and radio detections of the cores. Additionally, we place constraints on the galaxies' systemic redshifts via HeII lambda 1640 lines seen with the Multi-Unit Spectroscopic Explorer. We detect faint [CI] emission in four out of seven sources. In two of these galaxies, we discover narrow-line emission of full width at half-maximum less than or similar to 100 km s(-1) that may trace emission from bright kpc-scale gas clouds within the interstellar medium (ISM). In the other two [CI]-detected galaxies, line dispersions range from similar to 100-600 km s(-1) and may be tracing the rotational component of the cold gas. Overall, the [CI] line luminosities correspond to H-2 masses of M-H2,[CI]similar or equal to(0.5-3)x10(10) M-circle dot for the detections and M-H2,M-[CI]<0.65x10(10) M-circle dot for the [CI] non-detections in three out of seven galaxies within the sample. The molecular gas masses in our sample are relatively low in comparison to previously reported measures for similar galaxies that are M-H2,M-[CI]similar or equal to(3-4)x10(10) M-circle dot. Our results imply that the observed faintness in carbon emission is representative of a decline in molecular gas supply from previous star formation epochs and/or a displacement of molecular gas from the ISM due to jet-powered outflows.