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Atoms 2017, 5(4), 43; doi:10.3390/atoms5040043

Models of Emission-Line Profiles and Spectral Energy Distributions to Characterize the Multi-Frequency Properties of Active Galactic Nuclei

1
Department of Physics and Astronomy, University of Padua, Vicolo dell’Osservatorio 3, 35122 Padova, Italy
2
Astronomical Observatory of Brera, National Institute of Astrophysics (INAF), Via Bianchi 46, 23807 Merate, Italy
Current address: Vicolo dell’Osservatorio 3, 35122 Padova, Italy.
These authors contributed equally to this work.
*
Author to whom correspondence should be addressed.
Received: 10 September 2017 / Revised: 22 October 2017 / Accepted: 23 October 2017 / Published: 6 November 2017
(This article belongs to the Special Issue Spectral Line Shapes in Astrophysics and Related Topics)
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Abstract

The spectra of active galactic nuclei (AGNs) are often characterized by a wealth of emission lines with different profiles and intensity ratios that lead to a complicated classification. Their electromagnetic radiation spans more than 10 orders of magnitude in frequency. In spite of the differences between various classes, the origin of their activity is attributed to a combination of emitting components, surrounding an accreting supermassive black hole (SMBH), in the unified model. Currently, the execution of sky surveys, with instruments operating at various frequencies, provides the possibility to detect and to investigate the properties of AGNs on very large statistical samples. As a result of the spectroscopic surveys that allow the investigation of many objects, we have the opportunity to place new constraints on the nature and evolution of AGNs. In this contribution, we present the results obtained by working on multi-frequency data, and we discuss their relations with the available optical spectra. We compare our findings with the AGN unified model predictions, and we present a revised technique to select AGNs of different types from other line-emitting objects. We discuss the multi-frequency properties in terms of the innermost structures of the sources. View Full-Text
Keywords: galaxies: active; galaxies: nuclei; line: profiles; quasars: emission lines; catalogs; surveys galaxies: active; galaxies: nuclei; line: profiles; quasars: emission lines; catalogs; surveys
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).

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MDPI and ACS Style

La Mura, G.; Berton, M.; Chen, S.; Chougule, A.; Ciroi, S.; Congiu, E.; Cracco, V.; Frezzato, M.; Mordini, S.; Rafanelli, P. Models of Emission-Line Profiles and Spectral Energy Distributions to Characterize the Multi-Frequency Properties of Active Galactic Nuclei. Atoms 2017, 5, 43.

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