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Rapid black hole growth at the dawn of the Universe : Super-Eddington Quasar at z=6.6.

Tang, Ji-Jia and Goto, Tomotsugu and Ohyama, Youichi and Jin, Chichuan and Done, Chris and Lu, Ting-Yi and Hashimoto, Tetsuya and Eser, Ece Kilerci and Chiang, Chia-Ying and Kim, Seong Jin (2019) 'Rapid black hole growth at the dawn of the Universe : Super-Eddington Quasar at z=6.6.', Monthly notices of the Royal Astronomical Society., 484 (2). pp. 2575-2586.

Abstract

We present the analysis of a new near-infrared (NIR) spectrum of a recently discovered z = 6.621 quasar PSO J006 + 39 in an attempt to explore the early growth of supermassive black holes (SMBHs). This NIR (rest-frame ultraviolet, UV) spectrum shows blue continuum slope and rich metal emission lines in addition to Lyα line. We utilize the MgII line width and the rest-frame luminosity L3000A˚ to find the mass of SMBH (MBH) to be ∼108M⊙⁠, making this one of the lowest mass quasars at high redshift. The power-law slope index (αλ) of the continuum emission is −2.94 ± 0.03, significantly bluer than the slope of αλ = −7/3 predicted from standard thin disc models. We fit the spectral energy distribution (SED) using a model which can fit local SMBHs, which includes warm and hot Comptonization powered by the accretion flow as well as an outer standard disc. The result shows that the very blue slope is probably produced by a small radial (∼230 gravitational radius, Rg) extent of the standard accretion disc. All plausible SED models require that the source is super-Eddington (Lbol/LEdd ≳ 9), so the apparently small disc may simply be the inner funnel of a puffed up flow, and clearly the SMBH in this quasar is in a rapid growth phase. We also utilize the rest-frame UV emission lines to probe the chemical abundance in the broad-line region (BLR) of this quasar. We find that this quasar has super solar metallicity through photoionization model calculations.

Item Type:Article
Full text:(AM) Accepted Manuscript
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Status:Peer-reviewed
Publisher Web site:https://doi.org/10.1093/mnras/stz134
Publisher statement:© 2019 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society
Date accepted:08 January 2019
Date deposited:09 January 2019
Date of first online publication:12 January 2019
Date first made open access:No date available

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