HYPERION. Merger and outflow in the most luminous $z>6$ quasar

Author:

R. Tripodi, J. Scholtz, R. Maiolino, S. Fujimoto, S. Carniani, J. D. Silverman, C. Feruglio, M. Ginolfi, L. Zappacosta, T. Costa, G. C. Jones, E. Piconcelli, M. Bischetti, F. Fiore

Keyword:

Astrophysics, Astrophysics of Galaxies, Astrophysics of Galaxies (astro-ph.GA)

journal:

date:

2023-06-01 16:00:00

Abstract

We present ALMA deep observations of the [CII] 158 $\mu$m emission line and the continuum at 253 GHz and 99 GHz towards SDSS J0100+2802 at $z\simeq 6.3$, the most luminous QSO at z$>$6. It belongs to the HYPERION sample of luminous QSOs at $z\sim 6-7.5$. The observations (at 2.2$''$ resolution in band 3 and 0.9$''$ resolution in band 6) are optimized to detect extended emission around the QSO. We detect a merging, tidally disrupted companion both in [CII] and in continuum, stretching on scales up to 20 kpc from the quasar, with a knotty morphology. For the newly-detected companion we estimate a dust mass of $M_{\rm dust}=(0.6-4.3)\times 10^7\ \rm M_\odot$, an SFR in the range $[43-402]\ \rm M_\odot$, that is remarkably similar to the SFR of the QSO, and a neutral gas mass of $M_{\rm HI}=3.3\times 10^9\ \rm M_{\odot}$, suggesting that both the QSO and its companion are gas rich and that the major merging may be at the origin of the boosted star formation. This close merging companion is undetected by deep JWST imaging observations, supporting the effectiveness of ALMA in detecting dust obscured sources especially in the vicinity of optically bright quasars. We also detect a broad blueshifted component in the [CII] spectrum aligned with the radio jet of the QSO, suggesting that this may be the first detection of a radio jet - driven outflow at such high redshift. We estimate a mass outflow rate in the range $\dot{M}_{\rm out}=(115-269)\ \rm M_\odot\ yr^{-1}$. The outflow energetics is similar to that of ionized outflows found in other QSOs host at lower redshift, and the low momentum loading factor suggests that this outflow would not be very effective in removing the gas from the entire galaxy. These results highlight the importance of deep medium-resolution ALMA observations for the study of QSOs and their environment at the Epoch of Reionization.

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