Euclid Quick Data Release (Q1). Optical and near-infrared identification and classification of point-like X-ray selected sources

To better understand the role of active galactic nuclei (AGN) in galaxy evolution, it is crucial to work with a complete and pure AGN sample. X-ray surveys are key to doing so, but their larger positional uncertainties complicate counterpart (CTP) association, further compounded by the limited availability of deep, uniform multi-wavelength ancillary data. Euclid is revolutionising this identification effort, offering extensive coverage of nearly the entire extragalactic sky, particularly in the near-infrared bands, where AGN are more easily detected. Using the first Euclid Quick Data Release (Q1), we validated the methods for identifying and classifying Euclid CTPs of known point-like sources from major X-ray surveys, including Chandra and eROSITA. Using Bayesian statistics, combined with machine learning (ML), as incorporated in the algorithm NWAY we identified the CTPs of 11,286 X-ray sources from the three X-ray telescopes. For the large majority of 10,194 sources, the association is unique, with the remaining ∼ 10% of multi-CTP cases equally split between and eROSITA. Six percent of the Euclid CTPs are detected in more than one X-ray survey. We then used ML to distinguish between Galactic (8%) and extragalactic (92%) sources. We computed photo-zs using deep learning for the 9259 sources detected in the tenth data release of the DESI Legacy Survey, reaching an accuracy and a fraction of outliers of roughly 5%. Based on their X-ray luminosities, all CTPs identified as extragalactic are classified as AGN, most of which appear as type I AGN according to their hardness ratios. With this paper, we release our catalogue, which includes identifiers, basic X-ray properties, the reliability of the associations, and additional property extensions, such as Galactic- or extragalactic classifications and photometric/spectroscopic redshifts. We also provide probabilities for sub-selecting the sample based on purity and completeness, in order to allow users to tailor the sample according to their specific needs.

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Publication Details

Journal
Astronomy and Astrophysics
Published
2025-08-28
DOI
https://doi.org/10.1051/0004-6361/202554616
Citations
1
Primary Topic
Galaxies: Formation, Evolution, Phenomena
Type
article
Field-Weighted Citation Impact
1.15

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article

Euclid Quick Data Release (Q1). Optical and near-infrared identification and classification of point-like X-ray selected sources

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1 citations
Astronomy and Astrophysics
Galaxies: Formation, Evolution, Phenomena
1.15
article

Euclid Quick Data Release (Q1). Optical and near-infrared identification and classification of point-like X-ray selected sources

R. P. Saglia, G. Sirri, R Nakajima, J. Steinwagner, Y. Copin, J.J Diaz, C. Baccigalupi, S. V. H. Haugan, R. Massey, S. Andreon, C. Neissner, R. Toledo-Moreo, M. Huertas-Company, M. Meneghetti, J.W Nightingale, H. Hildebrandt, M. Martinelli, M. Salvato, E. Romelli, A. Cimatti, M Kümmel, B Sartoris, N. Martinet, L. Moscardini, V. Allevato, J. Väliviita, P. Schneider, A. Bonchi, S. Escoffier, J Brinchmann, L Blot, B. Gillis, W. Gillard, M Sahlén, V. Scottez, F. De Paolis, R. B. Metcalf, J. Rhodes, A. Hornstrup, L. Conversi, S. Fotopoulou, Francesco Shankar, M. Giulietti, S. Marcin, F. M. Zerbi, Hermine Landt, M. Béthermin, A. Balestra, E. Branchini, B. Altieri, A. Secroun, M. Farina, F. Mannucci, M Jhabvala, A. Venhola, S Dusini, V. Kansal, S. Ligori, L. Legrand, R. Farinelli, F. Giacomini, C. Valieri, Yuhong Fang, E. Franceschi, J.A Schewtschenko, K. Pedersen, S. Casas, M. Siudek, Pardis Simon, N. A. Walton, S. Davini, Antonio M. Mora, C. Porciani, R. Cabanac, Savvas Nesseris, S. Ferriol, Z. Sakr, F. Hormuth, L. Legrand, S. Mei, K. Kiiveri, LAURENCE C. SMITH, A. Blanchard, K. C. Chambers, F. Finelli⋆, M. Melchior, R. Rébolo, G. Verdoes Kleijn, R Farinelli, M. Sereno, E. Keihänen, D. Potter, P Vielzeuf, P. C. Schneider, M. Martinelli, R. Nakajima, S. Cavuoti, A da Silva, M. Frailis, S Camera, W.G Hartley, F. Grupp, P. Hudelot, C. Carbone, K. Paterson, S. Kermiche, Arthur Loureiro, F Caro, E. Soubrie, E Sarpa, M. Castellano, J. M. Diego, Elisabeta Lusso, Y. Mellier, O. Mansutti, A.G. Sánchez, P. B. Lilje, A. Fontana, S. Paltani, M. Viel, A.M.C Le Brun, E. Zucca, O. Cucciati, C. Burigana, E. Branchini, M. Siudek, S. Kermiche, F Grupp, F. Atrio‐Barandela, H. M. Courtois, G. Polenta, F. Cogato, D Sciotti, Yun Wang, S. Tosi, A. Da Silva, L. Maurin, J.E. Kajava, Y. W. Kang, G de Lucia, M. D. Seiffert, M. Roncarelli, I. Tutusaus, G Leroy, N. Aghanim, G. Meylan, S. Paltani, W. Holmes, D. Maino, X. Dupac, C. Hernández-Monteagudo, M. Baldi, L. Popa, F. Shankar, I. Tereno, V. Pettorino, A. Zacchei, P Battaglia, P Fosalba, L. Valenziano, G. Morgante, H. Kurki‐Suonio, M. Wiesmann, C. Hernández-Monteagudo, G. Testera, L Stanco, C. Baccigalupi, A. N. Taylor, K Benson, M. Bolzonella, J.A. Escartin Vigo, B. Kubik, D. Di Ferdinando, M. Tucci, H.M Courtois, P Monaco, R. Saglia, S. Fotopoulou, N. Fourmanoit, L Valenziano, M. Tucci, A. Zacchei, F. Gianotti, M. N. Bremer, C.M Gutierrez, G Mainetti, C. Dolding, M Guidi, A Finoguenov, H. Böhringer, M. Kümmel, R. Rebolo, X. Dupac, G. Congedo, A. Mora, T. Matamoro Zatarain, L. Leuzzi
article en
1 citations

Abstract

To better understand the role of active galactic nuclei (AGN) in galaxy evolution, it is crucial to work with a complete and pure AGN sample. X-ray surveys are key to doing so, but their larger positional uncertainties complicate counterpart (CTP) association, further compounded by the limited availability of deep, uniform multi-wavelength ancillary data. Euclid is revolutionising this identification effort, offering extensive coverage of nearly the entire extragalactic sky, particularly in the near-infrared bands, where AGN are more easily detected. Using the first Euclid Quick Data Release (Q1), we validated the methods for identifying and classifying Euclid CTPs of known point-like sources from major X-ray surveys, including Chandra and eROSITA. Using Bayesian statistics, combined with machine learning (ML), as incorporated in the algorithm NWAY we identified the CTPs of 11,286 X-ray sources from the three X-ray telescopes. For the large majority of 10,194 sources, the association is unique, with the remaining ∼ 10% of multi-CTP cases equally split between and eROSITA. Six percent of the Euclid CTPs are detected in more than one X-ray survey. We then used ML to distinguish between Galactic (8%) and extragalactic (92%) sources. We computed photo-zs using deep learning for the 9259 sources detected in the tenth data release of the DESI Legacy Survey, reaching an accuracy and a fraction of outliers of roughly 5%. Based on their X-ray luminosities, all CTPs identified as extragalactic are classified as AGN, most of which appear as type I AGN according to their hardness ratios. With this paper, we release our catalogue, which includes identifiers, basic X-ray properties, the reliability of the associations, and additional property extensions, such as Galactic- or extragalactic classifications and photometric/spectroscopic redshifts. We also provide probabilities for sub-selecting the sample based on purity and completeness, in order to allow users to tailor the sample according to their specific needs.

Astronomy and Astrophysics
Délégation Paris 7 (FR), Université Paris Cité (FR), Université de Lille (FR), Commissariat à l'Énergie Atomique et aux Énergies Alternatives (FR), Centre National d'Études Spatiales (FR), Institut d'Astrophysique de Paris (FR), European Space Agency (FR), Laboratoire AstroParticule et Cosmologie (FR), Observatoire astronomique de Strasbourg (FR), CEA Grenoble (FR), Astrophysique, Instrumentation et Modélisation (FR), Janssen (France) (FR), Laboratoire Univers et Théories (FR), Centre de physique des particules de Marseille (FR), Laboratoire d’Astrophysique de Marseille (FR), Institut d'Astrophysique Spatiale (FR), Laboratoire d’Etudes du Rayonnement et de la Matière en Astrophysique et Atmosphères (FR), CEA Cadarache (FR), Lagrange Laboratory (FR), Château Gombert (FR), CEA Paris-Saclay (FR), Laboratoire de Physique Subatomique et de Cosmologie (FR), Centre de Calcul de l’Institut National de Physique Nucléaire et de Physique des Particules (FR), Institute of Nuclear Physics of Lyon (FR), Institut de Recherche sur les Lois Fondamentales de l'Univers (FR), Institut de Recherche en Astrophysique et Planétologie (FR), Institut de Physique des 2 Infinis de Lyon (FR)
National Aeronautics and Space Administration, European Space Agency, Eberhard Karls Universität Tübingen, Generalitat de Catalunya, Magyar Tudományos Akadémia, Agenzia Spaziale Italiana, Max-Planck-Gesellschaft, Universität Hamburg, National Astronomical Observatory of Japan, Rheinische Friedrich-Wilhelms-Universität Bonn, Agenția Spațială Română, Leibniz-Institut für Astrophysik Potsdam, Norsk Romsenter, Institut de Física d'Altes Energies, Leibniz-Gemeinschaft, Fundação para a Ciência e a Tecnologia, Russian Academy of Sciences, Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas, Agencia Estatal de Investigación
Openalex Percentile: Top 17%
Galaxies: Formation, Evolution, Phenomena
1.15
DOIOpen Access PDFOpenAlex
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