Oral Presentation
Ongoing and fossil large scale outflows detected in a high-redshift radio galaxy: ALMA [CII] observation of TN J0924-2201 at z=5.17
Presenter: Kianhong Lee (Tohoku University/NAOJ)
High-redshift radio galaxies are massive star-forming galaxies with powerful radio jets, often located on or below the star-forming main sequence of galaxies. This suggests that they are in the process of being quenched.
TN J0924-2201 is one of the most distant known radio galaxies, associated with three CO(1-0)-detected companions at z~5.2.
We present ALMA observations of [CII] line and the corresponding 1 mm continuum emission of TN J0924-2201.
While obtaining the [CII] line and 1mm continuum emission at the host galaxy, our observations revealed no detection at the positions of the three CO(1-0) companions.
The derived systematic redshift z_[CII] of the host galaxy from the [CII] line is 5.17, indicating a blueshift than the Lya-derived redshift by a velocity offset of ~1000 km/s, marking the largest velocity offset between [CII] line and Lya line recorded at z>5 to date. Within the host galaxy, we identified an extended [CII] structure with a velocity of ~500 km/s, suggestive of an outflow. This finding aligns with the shell outflow model, providing consistency with the observed large velocity offset of Lya.
Applying the PDR model, our analysis indicates that the three massive CO(1-0) companions exhibit high density and a weak radiation field. Assuming they are also outflow, their velocities of ~1500 km/s surpass the escape velocity of a 10^13 Msun halo, implying the removal of molecular gas from the host galaxy. These results collectively point towards a distinctive phase in galaxy evolution occurring in a radio galaxy.
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