2023/06/02 by Roberta Tripodi, Tripodi, R., Jan Scholtz +25
Physics and Astronomy · #Galaxies: Formation, Evolution, Phenomena #Cosmology and Gravitation Theories #Astronomy and Astrophysical Research
paper · pdf · doi:10.48550/arxiv.2306.01644
We present ALMA deep observations of the [CII] 158 μm emission line and the continuum at 253 GHz and 99 GHz towards SDSS J0100+2802 at z≃ 6.3, the most luminous quasi-stellar object (QSO) at z>6. J0100+2802 belongs to the HYPERION sample of luminous QSOs at z∼ 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 an interacting, tidally disrupted companion both in [CII], peaking at z∼ 6.332, and in continuum, stretching on scales up to 20 kpc from the quasar, with a knotty morphology. The higher velocity dispersion in the direction of the companion emission and the complex morphology of tidally stretched galaxy suggest a possible ongoing or future merger. For the newly-detected companion we derive a range of dust mass, M\rm dust=(0.3-2.6)× 107 \rm M_\odot, and of star formation rate, SFR=[35-344] \rm M_\odot. This shows that both the QSO and its companion are gas rich and that a major merger may be at the origin of the boosted star formation. We also detect a broad blueshifted component in the [CII] spectrum, that we interpret as a gaseous outflow for which we estimate a mass outflow rate in the range M\rm out=(118-269) \rm M_\odot yr-1. J0100+2802 was recently found to reside in a strong overdensity, however this close companion remained undetected by both previous higher resolution ALMA observations and by JWST-NIRCAM imaging. Our results highlight the importance of deep medium-resolution ALMA observations for the study of QSOs and their environment at the Epoch of Reionization.