Abstract
Using the SDSS spectroscopy, we have carried out fine optical spectral classification for activity types for 710 AGN candidates. These objects come from a larger sample of some 2,500 candidate AGN using pre-selection by various samples; bright objects of the Catalog of Quasars and Active Galactic Nuclei, AGN candidates among X-ray sources, optically variable radio sources, IRAS extragalactic objects, etc. A number of papers have been published with the results of this spectral classification. More than 800 QSOs have been identified and classified, including 710 QSOs, Seyferts and Composites. The fine classification shows that many QSOs show the same features as Seyferts, i.e., subtypes between S1 and S2 (S1.2, S1.5, S1.8 and S1.9). We have introduced subtypes for the QSOs: QSO1.2, QSO1.5, QSO1.8, QSO1.9, though the last subtype does not appear in SDSS wavelength range due to mostly highly redshifted Hα (the main line for identification of the 1.9 subtype). Thus, independent of the luminosity (which serves as a separator between QSOs and Seyferts), AGN show the same features. We also have classified many objects as Composites, spectra having composite characteristics between Sy and LINERs, Sy and HII or LINERs and HII; in some cases all three characteristics appear together resulting as Sy/LINER/HII subtype. The QSOs subtypes together with Seyfert ones allow to follow AGN properties along larger redshift range expanding our knowledge on the evolution of AGN to more distant Universe represented by QSOs.
Highlights
Active Galaxies, including both Active Galactic Nuclei (AGN) and Starbursts (SB) are the most interesting objects in extragalactic astronomy and they are especially crucial for evolution of galaxies, as well as for understanding radiation mechanisms
An automated classification system and software are necessary that will take into account possible broad lines, carry out decomposition, measure the narrow lines to put on diagnostic diagrams
Our conclusion is that both software or a combination of both methods should be used for the full classification and our scheme should be incorporated in these methods having possibly the best description of all features of various subtypes of the AGN zoo
Summary
Active Galaxies, including both Active Galactic Nuclei (AGN) and Starbursts (SB) are the most interesting objects in extragalactic astronomy and they are especially crucial for evolution of galaxies, as well as for understanding radiation mechanisms. S1.2: Spectra of AGN, which share parameters that are intermediate between those of classical S1 and S2 galaxies, i.e., both broad and narrow components are present for permitted lines (in our case Hα and Hβ lines display such profiles, Osterbrock, 1980), broad lines are stronger, and 2.0 < Hβ/[OIII]5007 < 5.0 (Winkler, 1992). S1.8: AGN that share parameters that are intermediate between those of classical S1 and S2 galaxies; they have relatively weak broad Hα and Hβ components superposed on strong narrow lines, and Hβ/[OIII]5007 < 0.333 (Winkler, 1992). S1.9: Spectra of AGN that share parameters that are intermediate between those of classical S1 and S2 galaxies; they have relatively weak broad Hβ component superposed on a strong narrow line. We have used the software SPECTRAI (Véron et al, 1980)
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