The WISSH quasars project. V. ALMA reveals the assembly of a giant galaxy around a z = 4.4 hyper-luminous QSO

Bischetti, M.M.BischettiPICONCELLI, EnricoEnricoPICONCELLIFeruglio, ChiaraChiaraFeruglioDuras, F.F.DurasBONGIORNO, ANGELAANGELABONGIORNOCarniani, S.S.CarnianiMarconi, AlessandroAlessandroMarconiPappalardo, C.C.PappalardoSchneider, R.R.SchneiderTravascio, A.A.TravascioVALIANTE, ROSAROSAVALIANTEVIETRI, GIUSTINAGIUSTINAVIETRIZAPPACOSTA, LucaLucaZAPPACOSTAFiore, F.F.Fiore2020-10-192020-10-1920180004-6361http://hdl.handle.net/20.500.12386/27872We present an ALMA high-resolution (0.18″ × 0.21″) observation of the 840 μm continuum and [CII] λ157.74 μm line emission in the WISE-SDSS selected hyper-luminous (WISSH) quasi-stellar object (QSO) J1015+0020, at z ∼ 4.4. Our analysis reveals an exceptional overdensity of [CII]-emitting companions with a very small (<150 km s-1) velocity shift with respect to the QSO redshift. We report the discovery of the closest companion observed so far in submillimetre observations of high-z QSOs. It is only 2.2 kpc distant and merging with J1015+0020, while two other [CII] emitters are found at 8 and 17 kpc. Two strong continuum emitters are also detected at <3.5 arcsec from the QSO. They are likely associated with the same overdense structure of J1015+0020, as they exceed by a factor of 100 the number of expected sources, considering the log(N)-log(S) at 850 μm. The host galaxy of J1015+0020 shows a star formation rate (SFR) of about 100 M☉ yr-1, while the total SFR of the QSO and its companion galaxies is a factor of ∼10 higher, indicating that substantial stellar mass assembly at early epochs may have taken place in the QSO satellites. For J1015+0020 we computed a black hole mass MBH ∼ 6 × 109 M☉. As we resolve the [CII] emission of the QSO, we can compute a dynamical mass of Mdyn ∼ 4 × 1010 M☉. This translates into an extreme ratio Mdyn/MBH ∼ 7, i.e. two orders of magnitude smaller than what is typically observed in local galaxies. The total stellar mass of the QSO host galaxy plus the [CII] emitters in the ALMA field of view already exceeds 1011 M☉ at z ∼ 4.4. These sources will likely merge and develop into a giant galaxy of ∼1.3 × 1012 M☉. Under the assumption of constant Ṁacc or λEdd equal to the observed values, we find that the growth timescale of the host galaxy of J1015+0020 is comparable or even shorter than that inferred for the SMBH. Based on data from ALMA cycle 4 program 2016.1.00718.S.STAMPAenThe WISSH quasars project. V. ALMA reveals the assembly of a giant galaxy around a z = 4.4 hyper-luminous QSOArticle10.1051/0004-6361/2018332492-s2.0-85054068894000445285100002https://www.aanda.org/articles/aa/abs/2018/09/aa33249-18/aa33249-18.html2018A&A...617A..82BFIS/05 - ASTRONOMIA E ASTROFISICAERC sectors::Physical Sciences and Engineering::PE9 Universe sciences: astro-physics/chemistry/biology; solar systems; stellar, galactic and extragalactic astronomy, planetary systems, cosmology, space science, instrumentation