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Open AccessArticle

Broad UV Emission Lines in Type-1 Active Galactic Nuclei: A Note on Spectral Diagnostics and the Excitation Mechanism

1
National Institute for Astrophysics (INAF), Astronomical Observatory of Padova, IT-35122 Padova, Italy
2
Instituto de Astrofisíca de Andalucía, IAA-CSIC, Glorieta de la Astronomia s/n, E-18008 Granada, Spain
3
Dipartimento di Fisica & Astronomia “Galileo Galilei”, Università di Padova, IT-35122 Padova, Italy
4
Center for Theoretical Physics (Polish Academy of Sciences), Al. Lotnikó w 32/46, 02-668 Warsaw, Poland
5
Nicolaus Copernicus Astronomical Center (Polish Academy of Sciences), ul. Bartycka 18, 00-716 Warsaw, Poland
*
Author to whom correspondence should be addressed.
Received: 9 November 2020 / Revised: 8 December 2020 / Accepted: 9 December 2020 / Published: 18 December 2020
(This article belongs to the Section Atomic, Molecular and Nuclear Spectroscopy and Collisions)
This paper reviews several basic emission properties of the UV emission lines observed in the spectra of quasars and type-1 active galactic nuclei, mainly as a function of the ionization parameter, metallicity, and density of the emitting gas. The analysis exploits a general-purpose 4D array of the photoionization simulations computed using the code CLOUDY, covering ionization parameter in the range 104.510+1.0, hydrogen density nH1071014 cm−3, metallicity Z between 0.01 and 100 Z, and column density in the range 10211023 cm−2. The focus is on the most prominent UV emission lines observed in quasar spectra, namely Nvλ1240, Siivλ1397, Oiv]λ1402, Civλ1549, Heiiλ1640, Aliiiλ1860, Siiii]λ1892, and Ciii]λ1909, and on the physical conditions under which electron-ion impact excitation is predicted to be the dominant line producer. Photoionization simulations help constrain the physical interpretation and the domain of applicability of spectral diagnostics derived from measurements of emission line ratios, reputed to be important for estimating the ionization degree, density, and metallicity of the broad line emitting gas, as well as the relative intensity ratios of the doublet or multiplet components relevant for empirical spectral modeling. View Full-Text
Keywords: atomic processes; UV spectroscopy; ionized gas; broad line region atomic processes; UV spectroscopy; ionized gas; broad line region
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MDPI and ACS Style

Marziani, P.; del Olmo, A.; Perea, J.; D’Onofrio, M.; Panda, S. Broad UV Emission Lines in Type-1 Active Galactic Nuclei: A Note on Spectral Diagnostics and the Excitation Mechanism. Atoms 2020, 8, 94. https://0-doi-org.brum.beds.ac.uk/10.3390/atoms8040094

AMA Style

Marziani P, del Olmo A, Perea J, D’Onofrio M, Panda S. Broad UV Emission Lines in Type-1 Active Galactic Nuclei: A Note on Spectral Diagnostics and the Excitation Mechanism. Atoms. 2020; 8(4):94. https://0-doi-org.brum.beds.ac.uk/10.3390/atoms8040094

Chicago/Turabian Style

Marziani, Paola; del Olmo, Ascension; Perea, Jaime; D’Onofrio, Mauro; Panda, Swayamtrupta. 2020. "Broad UV Emission Lines in Type-1 Active Galactic Nuclei: A Note on Spectral Diagnostics and the Excitation Mechanism" Atoms 8, no. 4: 94. https://0-doi-org.brum.beds.ac.uk/10.3390/atoms8040094

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