DOE OSTI · 3010591
Beyond traditional diagnostics: Identifying active galactic nuclei using spectral energy distribution fitting in DESI data
Abstract
Active galactic nuclei (AGN) are typically identified through their distinctive X-ray or radio emissions, mid-infrared (MIR) colors, or emission lines. However, each method captures different subsets of AGN due to signal-to-noise (S/N) limitations, redshift coverage, and extinction effects, underscoring the necessity for a multiwavelength approach for comprehensive AGN samples. This study explores the effectiveness of spectral energy distribution (SED) fitting as a robust method for AGN identification. Using CIGALE optical-MIR SED fits on DESI Early Data Release galaxies, we compare SED-based AGN selection (AGNFRAC ≥ 0.1) with traditional methods including BPT diagrams, WISE colors, X-ray, and radio diagnostics. The SED fitting identifies ∼70% of narrow- and broad-line AGN and 87% of WISE-selected AGN. Incorporating high S/N WISE photometry reduces star-forming galaxy contamination from 62% to 15%. Initially, ∼50% of SED-AGN candidates are undetected by standard methods, but additional diagnostics classify ∼85% of these sources, revealing low-ionization nuclear emission-line regions and retired galaxies potentially representing evolved systems with weak AGN activity. Further spectroscopic and multiwavelength analysis will be essential to determine the true AGN nature of these sources. SED fitting provides complementary AGN identification, unifying multiwavelength AGN selections. This approach enables more complete – albeit somewhat contaminated – AGN samples, which are essential for upcoming large-scale surveys where spectroscopic diagnostics may be limited.
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Siudek, M. [Universidad de La Laguna (ULL), Tenerife (Spain); Institute of Space Sciences (ICE, CSIC), Barcelona (Spain)] (ORCID:0000000229492155), Mezcua, M. [Institute of Space Sciences (ICE, CSIC), Barcelona (Spain); Institut d’Estudis Espacials de Catalunya (IEEC), Castelldefels (Spain)] (ORCID:000000034440259X), Circosta, C. [University College London (United Kingdom)], Maraston, C. [University of Portsmouth (United Kingdom)] (ORCID:0000000177113677), Moustakas, J. [Siena College, Loudonville, NY (United States)], Zou, H. [Chinese Academy of Sciences, Beijing (China)], Aguilar, J. [Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States)] (ORCID:000000030822452X), Ahlen, S. [Boston University, MA (United States)], Bianchi, D. [Università degli Studi di Milano (Italy); INAF-Osservatorio Astronomico di Brera, Milano (Italy)] (ORCID:0000000197120006), Brooks, D. [University College London (United Kingdom)] (ORCID:0000000284585047), Claybaugh, T. [Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States)], Dawson, K. S. [University of Utah, Salt Lake City, UT (United States)] (ORCID:0000000205533805), de la Macorra, A. [Universidad Nacional Autónoma de México (Mexico)], Dey, A. [NSF NOIRLab, Tucson, AZ (United States)] (ORCID:0000000249284003), Doel, P. [University College London (United Kingdom)], Forero-Romero, J. E. [Universidad de los Andes, Bogota (Colombia)] (ORCID:0000000228903725), Gaztañaga, E. [Institut d’Estudis Espacials de Catalunya (IEEC), Castelldefels (Spain); University of Portsmouth (United Kingdom); Institute of Space Sciences (ICE, CSIC), Barcelona (Spain)], Gontcho A Gontcho, S. [Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States)], Gutierrez, G. [Fermi National Accelerator Laboratory (FNAL), Batavia, IL (United States)] (ORCID:0000000308250517), Ishak, M. [University of Texas at Dallas, Richardson, TX (United States)], Juneau, S. [NSF NOIRLab, Tucson, AZ (United States)], Kirkby, D. [University of California, Irvine, CA (United States)] (ORCID:0000000288285463), Kisner, T. [Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States)], Kremin, A. [Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States)] (ORCID:0000000163567424), Lambert, A. [Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States)], Landriau, M. [Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States)], Le Guillou, L. [Sorbonne Université, Paris (France)] (ORCID:0000000171788868), Meisner, A. [NSF NOIRLab, Tucson, AZ (United States)], Miquel, R. [Institució Catalana de Recerca i Estudis Avançats, Barcelona (Spain); The Barcelona Institute of Science and Technology (Spain)] (ORCID:0000000266104836), Prada, F. [Instituto de Astrofísica de Andalucía (CSIC), Granada (Spain)], Pérez-Ràfols, I. [Universitat Politècnica de Catalunya, Barcelona (Spain)] (ORCID:0000000169790125), Rossi, G. [Sejong University, Seoul (Korea, Republic of)], Sanchez, E. [CIEMAT, Madrid (Spain)] (ORCID:0000000296468198), Schlegel, D. [Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States)] (ORCID:0000000250425088), Schubnell, M. [University of Michigan, Ann Arbor, MI (United States)], Seo, H. [Ohio University, Athens, OH (United States)] (ORCID:0000000265883508), Sprayberry, D. [NSF NOIRLab, Tucson, AZ (United States)], Tarlé, G. [University of Michigan, Ann Arbor, MI (United States)] (ORCID:0000000317040781), Weaver, B. A. [NSF NOIRLab, Tucson, AZ (United States)]. 2025-08-21. Beyond traditional diagnostics: Identifying active galactic nuclei using spectral energy distribution fitting in DESI data. https://doi.org/10.1051/0004-6361%2F202555463
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