1. Obscured AGN at 1.5 <z <3.0 from the zCOSMOS-deep Survey I. Properties of the emitting gas in the narrow-line region
- Author
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V. Mainieri, M. Bolzonella, Angela Bongiorno, E. Perez Montero, E. Zucca, Roberto Gilli, Simon J. Lilly, Anton M. Koekemoer, Christian Maier, Rongmon Bordoloi, V. Le Brun, Karina Caputi, M. Mignoli, G. Zamorani, Bianca Garilli, Andrea Cimatti, Cristian Vignali, Y. Peng, C. Diener, S. Bardelli, O. Le Fèvre, Anna Feltre, John D. Silverman, Francesco Calura, Istituto Nazionale di Astrofisica, European Research Council, National Key Research and Development Program (China), National Science Foundation (US), Astronomy, ITA, Institut d'Astrophysique de Paris (IAP), Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Centre de Recherche Astrophysique de Lyon (CRAL), École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Laboratoire d'Astrophysique de Marseille (LAM), and Aix Marseille Université (AMU)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)
- Subjects
ACTIVE GALACTIC NUCLEI ,EMISSION-LINES ,Active galactic nucleus ,Radio galaxy ,Metallicity ,Astrophysics::High Energy Astrophysical Phenomena ,MASS-METALLICITY RELATION ,galaxies: active ,galaxies [x-rays] ,CHEMICAL EVOLUTION ,RADIO GALAXIES ,Astrophysics ,Astrophysics::Cosmology and Extragalactic Astrophysics ,LUMINOSITY RELATIONSHIP ,01 natural sciences ,formation [line] ,SUPERMASSIVE BLACK-HOLES ,emission lines [quasars] ,0103 physical sciences ,STAR-FORMING GALAXIES ,fundamental parameters [galaxies] ,Emission spectrum ,010303 astronomy & astrophysics ,Astrophysics::Galaxy Astrophysics ,evolution [galaxies] ,Physics ,Supermassive black hole ,[SDU.ASTR]Sciences of the Universe [physics]/Astrophysics [astro-ph] ,010308 nuclear & particles physics ,NEBULAR EMISSION ,Astronomy and Astrophysics ,galaxies: fundamental parameters ,Astrophysics - Astrophysics of Galaxies ,FUNDAMENTAL RELATION ,Galaxy ,Redshift ,quasars: emission lines ,X-rays: galaxies ,[SDU]Sciences of the Universe [physics] ,Space and Planetary Science ,active [galaxies] ,Microturbulence ,line: formation ,galaxies: evolution - Abstract
The physics and demographics of high-redshift obscured active galactic nuclei (AGN) is still scarcely investigated. New samples of such objects, selected with different techniques, can provide useful insights into their physical properties. Aims. With the goal to determine the properties of the gas in the emitting region of type 2 AGN, in particular, the gas metal content, we exploit predictions from photoionization models, including new parameterizations for the distance of gas distribution from the central source and internal microturbulence in the emitting clouds, to interpret rest-frame UV spectral data. Methods. We selected a sample of 90 obscured (type 2) AGN with 1.45 ≤ z ≤ 3.05 from the zCOSMOS-deep galaxy sample by 5σ detection of the high-ionization C iv λ1549 narrow emission line. This feature in a galaxy spectrum is often associated with nuclear activity, and the selection effectiveness has also been confirmed by diagnostic diagrams based on utraviolet (UV) emission-line ratios. We applied the same selection technique and collected a sample of 102 unobscured (type 1) AGN. Taking advantage of the large amount of multiband data available in the COSMOS field, we investigated the properties of the Civ-selected type 2 AGN, focusing on their host galaxies, X-ray emission, and UV emission lines. Finally, we investigated the physical properties of the ionized gas in the narrow-line region (NLR) of this type 2 AGN sample by combining the analysis of strong UV emission lines with predictions from photoionization models. Results. We find that in order to successfully reproduce the relative intensity of UV emission lines of the selected high-z type 2 AGN, two new ingredients in the photoionization models are fundamental: small inner radii of the NLR (≈90 pc for LAGN = 1045 erg s−1 ), and the internal dissipative microturbulence of the gas-emitting clouds (with vmicr ≈ 100 km s−1 ). With these modified models, we compute the gas-phase metallicity of the NLR, and our measurements indicate a statistically significant evolution of the metal content with redshift. Finally, we do not observe a strong relationship between the NLR gas metallicity and the stellar mass of the host galaxy in our Civ-selected type 2 AGN sample.© ESO 2019, We acknowledge financial support from the agreement ASI-INAF n. 2017-14-H.O. A.F. acknowledges support from the ERC via an Advanced Grant under grant agreement no. 321323-NEOGAL and no. 339659- MUSICOS. A.C. acknowledges the support from the grants PRIN-MIUR 2015 and ASI n.I/023/12/0 and ASI n.2018-23-HH.0. Y.P. acknowledges National Key R&D Program of China Grant 2016YFA0400702, and NSFC Grant No. 11773001 and 11721303.
- Published
- 2019
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