2020ApJ...903...34A -
Astrophys. J., 903, 34-34 (2020/November-1)
Probing the nature of high-redshift weak emission line quasars: a young quasar with a starburst host galaxy.
ANDIKA I.T., JAHNKE K., ONOUE M., BANADOS E., MAZZUCCHELLI C., NOVAK M., EILERS A.-C., VENEMANS B.P., SCHINDLER J.-T., WALTER F., NEELEMAN M., SIMCOE R.A., DECARLI R., FARINA E.P., MARIAN V., PENSABENE A., COOPER T.M. and ROJAS A.F.
Abstract (from CDS):
We present the discovery of PSO J083.8371+11.8482, a weak emission line quasar with extreme star formation rate at z = 6.3401. This quasar was selected from Pan-STARRS1, UHS, and unWISE photometric data. Gemini/GNIRS spectroscopy follow-up indicates a Mg II-based black hole mass of MBH=(2.0–0.4+0.7)×109M☉ and an Eddington ratio of Lbol/LEdd=0.5–0.2+0.1, in line with an actively accreting supermassive black hole (SMBH) at z >= 6. Hubble Space Telescope imaging sets strong constraint on lens boosting, showing no relevant effect on the apparent emission. The quasar is also observed as a pure point source with no additional emission component. The broad-line region (BLR) emission is intrinsically weak and not likely caused by an intervening absorber. We found rest-frame equivalent widths of EW (Lyα+NV)rest=5.7±0.7Å, EW (CIV)rest≤ 5.8 Å (3σ upper limit), and EW (MgII)rest=8.7±0.7Å. A small proximity zone size (Rp=1.2±0.4 pMpc) indicates a lifetime of only tQ=10^3.4±0.7^ years from the last quasar phase ignition. ALMA shows extended [C II] emission with a mild velocity gradient. The inferred far-infrared luminosity (LFIR=(1.2±0.1)×1013L☉) is one of the highest among all known quasar hosts at z >= 6. Dust and [C II] emissions put a constraint on the star formation rate of SFR = 900-4900M☉yr–1, similar to that of a hyperluminous infrared galaxy. Considering the observed quasar lifetime and BLR formation timescale, the weak-line profile in the quasar spectrum is most likely caused by a BLR that is not yet fully formed rather than by continuum boosting by gravitational lensing or a soft continuum due to super-Eddington accretion.
Abstract Copyright:
© 2020. The American Astronomical Society. All rights reserved.
Journal keyword(s):
Quasars - Supermassive black holes - Active galactic nuclei - AGN host galaxies - Intergalactic medium - Reionization - Early universe
Simbad objects:
10
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