RT Journal Article
T1 Extinction and AGN over host galaxy contrast effects on the optical spectroscopic classification of AGN
A1 Barquín-González, L.
A1 Mateos, S.
A1 Carrera, F. J.
A1 Ordovás-Pascual, I.
A1 Alonso-Herrero, A.
A1 Caccianiga, A.
A1 Cardiel López, Nicolás
A1 Corral, A.
A1 Domínguez, R. M.
A1 García-Bernete, I.
A1 Mountrichas, G.
A1 Severgnini, P.
AB The optical spectroscopic classification of active galactic nuclei (AGN) into type 1 and type 2 can be understood in the frame of the AGN unification models. However, it remains unclear which physical properties are driving the classification into intermediate sub-types (1.0, 1.2, 1.5, 1.8, 1.9). To shed light on this issue, we present an analysis of the effect of extinction and AGN and host galaxy luminosities on sub-type determination for a sample of 159 X-ray selected AGN with a complete and robust optical spectroscopic classification. The sample spans a rest-frame 2–10 keV X-ray luminosity range of 10^(42)–10^(46) erg s^(−1) and redshifts between 0.05 and 0.75. From the fitting of their ultraviolet-to-mid-infrared spectral energy distributions, we extracted the observed AGN over total AGN+galaxy contrast, optical/ultraviolet line-of-sight extinction, as well as host galaxy and AGN luminosities. The observed contrast exhibits a clear decline with sub-type, distinguishing two main groups: 1.0–5 and 1.8–2. This difference is partly driven by an increase in extinction following the same trend. Nevertheless, 50% of 1.9s and 2s lack sufficient extinction to explain the lack of detection of broad emission lines, unveiling the necessity of an additional effect. Our findings show that 1.8–2s preferentially live in host galaxies with higher luminosities while displaying similar intrinsic AGN luminosities to 1.0–5s. Consequently, the AGN to host galaxy luminosity ratio diminishes, hindering the detection of the emission of the broad emission lines, resulting in the 1.8–2 classification of those with insufficient extinction. Thus, the combination of increasing extinction and decreasing AGN over galaxy luminosity ratio, mainly driven by an increasing host galaxy luminosity, constitutes the main reasons behind the sub-type classification into 1.0–5 and 1.8–2.
PB EDP Sciences. S A
SN 0004-6361
YR 2024
FD 2024
LK https://hdl.handle.net/20.500.14352/134889
UL https://hdl.handle.net/20.500.14352/134889
LA eng
NO Barquín-González, L., et al. «Extinction and AGN over host galaxy contrast effects on the optical spectroscopic classification of AGN». Astronomy & Astrophysics, vol. 687, julio de 2024, p. A159. DOI.org (Crossref), https://doi.org/10.1051/0004-6361/202348948.
NO © The Authors 2024.
NO Gobierno de España
NO ERDF A way of making Europe
NO UK Research & Innovation (UKRI)
NO Science & Technology Facilities Council (STFC)
NO European Space Agency
NO National Aeronautics & Space Administration (NASA)
NO Alfred P. Sloan Foundation
NO National Science Foundation (Estados Unidos)
NO United States Department of Energy (Estados Unidos)
NO Ministry of Education, Culture, Sports, Science and Technology, Japan (MEXT)
NO Max Planck Society
NO Higher Education Funding Council for England
NO European Organisation for Astronomical Research in the Southern hemisphere, Chile
DS Docta Complutense
RD 27 abr 2026