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arXiv · 2504.15357

ALMA reveals bright circumgalactic emission and a biconical outflow in z~6.4 quasar PSOJ183+05

Manuela Bischetti·Chiara Feruglio·Stefano Carniani·Valentina D'Odorico·Francesco Salvestrini·Fabrizio Fiore
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Abstract

Understanding gas flows between galaxies and their surrounding circum-galactic medium (CGM) is crucial to unveil the mechanisms regulating galaxy evolution, especially in the early Universe. However, observations of the CGM around massive galaxies at $z>6$ remain limited, particularly in the cold gas phase. In this work, we present multi-configuration ALMA observations of [CII]$\lambda158μ$m and millimetre continuum emission in the $z\sim6.4$ quasar PSOJ183+05. We find clumpy [CII] emission, tracing gas up to a $\sim6$ kpc radius, consistent with the interface region between the interstellar medium (ISM) and CGM. The [CII] kinematics shows a rotating disk and a high-velocity, biconical outflow extending up to 5 kpc. The inferred mass outflow rate is $\dot{M}_{\rm of}\sim930$ M$_\odot$ yr$^{-1}$, among the highest at $z>6$, and comparable to the star-formation rate. These findings suggest that quasar-driven outflows can rapidly transfer energy and momentum to the CGM, without immediately quenching star formation in the host galaxy ISM. This supports a delayed feedback scenario, in which outflows reshape CGM conditions and regulate future gas accretion over longer timescales. We find that neither the high-velocity component nor the extended CGM emission in PSOJ183+05 are recovered when using the high-resolution dataset alone, which may explain the conflicting results reported regarding [CII] sizes and the detection of outflows at $z\gtrsim6$. Combining multi-configuration ALMA data with observations from JWST and MUSE will be crucial to map the CGM across its different phases and build a comprehensive picture of the baryon cycle in the first massive galaxies.

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Manuela Bischetti, Chiara Feruglio, Stefano Carniani, Valentina D'Odorico, Francesco Salvestrini, Fabrizio Fiore. 2025-06-23. ALMA reveals bright circumgalactic emission and a biconical outflow in z~6.4 quasar PSOJ183+05. https://arxiv.org/abs/2504.15357

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