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arXiv · 2407.00977

Ongoing and fossil large-scale outflows detected in a high-redshift radio galaxy: [C II] observations of TN J0924$-$2201 at $z=5.174$

Kianhong Lee·Masayuki Akiyama·Kotaro Kohno·Daisuke Iono·Masatoshi Imanishi·Bunyo Hatsukade·Hideki Umehata·Tohru Nagao·Yoshiki Toba·Xiaoyang Chen·Fumi Egusa·Kohei Ichikawa·Takuma Izumi·Naoki Matsumoto·Malte Schramm·Kenta Matsuoka
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Abstract

We present Atacama Large Millimeter/submillimeter Array observations of the [C II] 158 $μ$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 $z_{\rm [C II]}=5.1736\pm0.0002$, indicating that the Ly$α$ line is redshifted by a velocity of $1035\pm10$ km s$^{-1}$, marking the largest velocity offset between the [C II] and Ly$α$ 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 $702\pm17$ km s$^{-1}$, which is close to the CIV line with a velocity of $500\pm10$ 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$α$. 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 $\sim1500$ km s$^{-1}$, outflowing molecular clouds induced by the AGN is the most plausible interpretation, and they may exceed the escape velocity of a $10^{13}\,M_{\odot}$ 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.

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Kianhong Lee, Masayuki Akiyama, Kotaro Kohno, Daisuke Iono, Masatoshi Imanishi, Bunyo Hatsukade, Hideki Umehata, Tohru Nagao, Yoshiki Toba, Xiaoyang Chen, Fumi Egusa, Kohei Ichikawa, Takuma Izumi, Naoki Matsumoto, Malte Schramm, Kenta Matsuoka. 2024-07-01. Ongoing and fossil large-scale outflows detected in a high-redshift radio galaxy: [C II] observations of TN J0924$-$2201 at $z=5.174$. https://arxiv.org/abs/2407.00977

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