EDP Sciences
Free access
Volume 367, Number 1, February III 2001
Page(s) 51 - 58
Section Extragalactic astronomy
DOI http://dx.doi.org/10.1051/0004-6361:20000418

A&A 367, 51-58 (2001)
DOI: 10.1051/0004-6361:20000418

Emission-line properties of MG 2016+112: A luminous obscured quasar at high redshift

T. Yamada1, S. Yamazaki1, M. Hattori1, G. Soucail2 and J.-P. Kneib2

1  Astronomical Institute, Tohoku University, Aoba-ku, Sendai 980-77, Japan
2  OMP, 14 Av. E. Belin, 31400 Toulouse, France

(Received 5 August 1999 / Accepted 27 November 2000 )

We present new high signal-to-noise ratio spectra of the components B and C of the gravitational lensing system MG 2016+112. We show that image C displays strong emission lines of Ly$\alpha$, NV, CIV, HeII, and CIII] redshifted to z=3.27, similar to images A and B. We examine the emission-line flux ratios in order to put constraints on the lens models as well as to investigate the intrinsic nature of MG 2016+112. The observed line ratios of B and C are consistent with those expected in the simple photo-ionization models for narrow-line region of active galactic nuclei (AGN) except for the enhanced NV lines. The line ratios difference of components B and C can be interpreted as a difference in ionization parameters. This result is consistent with lens model prediction that C is a fold image of a slightly outer part of the nucleus. MG 2016+112 is known to be very unique among the high-redshift AGN; it is neither an ordinary broad-line quasar nor a powerful radio galaxy as indicated by the width and flux ratio of the emission lines. Together with other observed properties discussed in literature, we argue that MG 2016+112 may be an obscured luminous radio-quiet quasar.

Key words: galaxies: active -- galaxies: quasars: emission lines -- galaxies: quasars: individual: MG 2016+112

Offprint request: T. Yamada, yamada@astr.tohoku.ac.jp

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