Ongoing and fossil large-scale outflows detected in a high-redshift radio galaxy: C II observations of TN J0924-2201 at z=5. 174

We present Atacama Large Millimeter/submillimeter Array observations of the C II 158 m line and the underlying continuum emission of TN J0924-2201, which is one of the most distant known radio galaxies at z>5. The C II line and 1-mm continuum emission are detected at the host galaxy. The systemic redshift derived from the C II line is z ₂ ₈₈=5. 17360. 0002, indicating that the Ly line is redshifted by a velocity of 103510 km s^-1, marking the largest velocity offset between the C II and Ly lines recorded at z>5 to date. In the central region of the host galaxy, we identified a redshifted substructure of C II with a velocity of 70217 km s^-1, which is close to the CIV line with a velocity of 50010 km s^-1. The position and the velocity offsets align with a model of an outflowing shell structure, consistent with the large velocity offset of Ly. The non-detection of C II and dust emission from the three CO (1--0) -detected companions indicates their different nature compared to dwarf galaxies based on the photodissociation region model. Given their large velocity of 1500 km s^-1, outflowing molecular clouds induced by the AGN is the most plausible interpretation, and they may exceed the escape velocity of a 10^13\, M_ halo. These results suggest that TN J0924-2201, with the ongoing and fossil large-scale outflows, is in a distinctive phase of removing molecular gas from a central massive galaxy in an overdense region in the early universe. A dusty HI absorber at the host galaxy is an alternative interpretation.