Fine classification of the emission-line spectra of active galaxies

Abstract

We refine the classification of galaxies by activity types based on a number of samples of objects having homogeneous optical medium resolution spectra from SDSS. SDSS spectra provide many spectral features and details that were not available before. Three diagnostic diagrams and eye examination have been used and the combined activity types have been derived. A fine classification scheme was developed, where QSOs have subtypes like Seyferts, Narrow Line QSOs are introduced, subclasses for Narrow Line Seyfert 1s are used and Composite spectrum objects have their subtypes. This classification scheme much better describes all fine details in the optical spectra and allows further study of active galaxies by the subtypes for better understanding the Unified model and the physical properties of AGN and Starbursts.

Homogeneous fine classification of Markarian galaxies based on SDSS medium-resolution spectroscopy

“…We carried out a thorough analysis and classification considering both SDSS tabular data (three diagnostic diagrams, DD1, DD2, and DD3, using line intensity ratios [OIII]/H β vs. The novelties of our study are as follows: -Homogeneous spectral classification for 779 Mrk galaxies based on the SDSS medium-resolution spectroscopy (on average much higher quality than the previously used ones); -Introduction of fine details (subtypes of objects) in the classification scheme based on the Mickaelian Fine Classification of Active Galaxies (Mickaelian et al 2022); -Correction of old incorrect or partly incorrect (misclassified) types and subtypes (mostly due to lower-quality spectra); -Spectral identification of Mrk galaxies into 2 QSOs, 49 classical Seyferts (BLS1), 17 NLS1s, 4 Sy2s, 12 LINERs, 11 AGN without definite type, 31 Composite spectrum objects, and 533 HII/Starbursts. Concerning the efficiency of our revised classification, we introduced proper classifications for 548 (out of 779) Mrk objects, which is 70.35% of the sample.…”

“…Given the importance of Markarian galaxies and their wide usage in various extragalactic studies, it was important to A174, page 6 of 9 have a homogeneous spectral classification for activity types, which became possible thanks to SDSS medium-resolution spectroscopy. Moreover, given our recently suggested fine classification (Mickaelian et al 2022), subtypes are also available for most of the objects, when it is allowed by the quality of spectra.…”

“…In a number of our papers we used the same approach to classify by activity types thousands of objects from various samples using SDSS medium-resolution spectra (Gyulzadyan et al 2017;Mickaelian et al 2018aMickaelian et al , 2022Abrahamyan et al 2018Abrahamyan et al , 2019Abrahamyan et al , 2020Paronyan et al 2019Paronyan et al , 2020Mikayelyan et al 2019;Abrahamyan 2020; Mickaelian Fine Classification of Active Galaxies 2022 1 ). Our approach is based on BPT diagrams (Baldwin et al 1981;Veilleux & Osterbrock 1987;Osterbrock 1980Osterbrock , 1981Winkler 1992;Véron-Cetty & Véron 2000); however, we used the most recent options of these diagrams (Kewley et al 2006;Reines et al 2013).…”

“…When no broad components are observed, the object is classified by the diagnostic diagrams. A detailed description of our developed scheme is given in Mickaelian et al (2022) and Mickaelian et al (2021), and on the dedicated webpage of our classification (Mickaelian Fine Classification of Active Galaxies 2022 1 ). The novelty of this classification scheme is the introduction of subtypes of the NLS1 and Composite spectrum objects.…”

“…We analyzed all these data and carried out our study based on them. This work utilizes the SDSS medium-resolution spectral classification of Mrk galaxies using our new classification scheme (Mickaelian et al 2022) to obtain a distribution and statistics of homogeneous activity types with their all possible fine details.…”