FORMATION OF HIGH-REDSHIFT (z>6) QUASARS DRIVEN BY NUCLEAR STARBURSTS
- National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588 (Japan)
Based on the physical model of a supermassive black hole (SMBH) growth via gas accretion in a circumnuclear disk (CND) proposed by Kawakatu and Wada, we describe the formation of high-z (z>6) quasars (QSOs) whose BH masses are M{sub BH}>10{sup 9} M{sub sun}. We derive the necessary conditions to form QSOs at z>6 by only gas accretion: (1) a large mass supply with M{sub sup}>10{sup 10} M{sub sun}from host galaxies to CNDs, because the final BH mass is only 1%-10% of the total supplied mass from QSO hosts. (2) High star formation efficiency for a rapid BH growth which is comparable to high-z starburst galaxies such as submillimeter galaxies. We also find that if the BH growth is limited by the Eddington accretion, the final BH mass is greatly suppressed when the period of mass supply from hosts, t{sub sup}, is shorter than the Eddington timescale. Thus, the super-Eddington growth is required for the QSO formation while t{sub sup}, which is determined by the efficiency of angular momentum transfer, is shorter than approx10{sup 8} yr. The evolution of the QSO luminosity depends on the redshift z {sub i} at which accretion onto a seed BH is initiated. In other words, the brighter QSOs at z>6 favor the late growth of SMBHs (i.e., z{sub i} approx 10) rather than early growth (i.e., z{sub i} approx 30). For z {sub i} approx 10, t{sub sup} approx = 10{sup 8} yr is shorter than that of the star formation in the CND. Thus, the gas in the CND can accrete onto a BH more efficiently, compared with the case for z {sub i} approx 30 (or t{sub sup} approx 10{sup 9} yr). Moreover, we predict the observable properties and the evolution of QSOs at z>6. In a QSO phase, there should exist a stellar rich massive CND, whose gas mass is about 10% of the dynamical mass inside approx0.1-1 kpc. On the other hand, in a phase where the BH grows (i.e., a proto-QSO phase), the proto-QSO has a gas-rich massive CND whose gas mass is comparable to the dynamical mass. Compared with the observed properties of the distant QSO SDSS J1148+5251 observed at z = 6.42, we predict that SDSS J1148+5251 corresponds to the scenario of the late growth of SMBH with z{sub i} approx 10, which is accompanied by a massive CNDs with M{sub g} approx 5 x 10{sup 10} M {sub sun} and the luminous nuclear starburst L{sub SB}at infrared band with L{sub SB} approx 10{sup 47} erg s{sup -1}. Moreover, we predict that the progenitor of SDSS J1148+5251 can be the super-Eddington object. These predictions can be verified by ALMA, SPICA, and JWST.
- OSTI ID:
- 21378153
- Journal Information:
- Astrophysical Journal, Vol. 706, Issue 1; Other Information: DOI: 10.1088/0004-637X/706/1/676; ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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