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Automated algorithms to build active galactic nucleus classifiers

Abstract: We present a machine learning model to classify active galactic nuclei (AGNs) and galaxies (AGN-galaxy classifier) and a model to identify type 1 (optically unabsorbed) and type 2 (optically absorbed) AGN (type 1/2 classifier). We test tree-based algorithms, using training samples built from the X-ray Multi-Mirror Mission?Newton (XMM?Newton) catalogue and the Sloan Digital Sky Survey (SDSS), with labels derived from the SDSS survey. The performance was tested making use of simulations and of cross-validation techniques. With a set of features including spectroscopic redshifts and X-ray parameters connected to source properties (e.g. fluxes and extension), as well as features related to X-ray instrumental conditions, the precision and recall for AGN identification are 94 and 93 per?cent, while the type 1/2 classifier has a precision of 74 per?cent and a recall of 80 per?cent for type 2 AGNs. The performance obtained with photometric redshifts is very similar to that achieved with spectroscopic redshifts in both test cases, while there is a decrease in performance when excluding redshifts. Our machine learning model trained on X-ray features can accurately identify AGN in extragalactic surveys. The type 1/2 classifier has a valuable performance for type 2 AGNs, but its ability to generalize without redshifts is hampered by the limited census of absorbed AGN at high redshift.

 Fuente: Monthly Notices of the Royal Astronomical Society, Volume 510, Issue 1, February 2022, Pages 161-176

 Editorial: Oxford University Press

 Año de publicación: 2022

 Nº de páginas: 16

 Tipo de publicación: Artículo de Revista

 DOI: https://doi.org/10.1093/mnras/stab3435

 ISSN: 0035-8711,1365-2966

 Url de la publicación: https://doi.org/10.1093/mnras/stab3435