June
2026
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2026A&A...711A..37E
Authors
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Euclid Collaboration
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Žerjal, M.
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Dominguez-Tagle, C.
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Vitas, N.
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Sedighi, N.
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Martín, E. L.
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Zapatero Osorio, M. R.
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Olivares, J.
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Muñoz Torres, S.
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Tsilia, S.
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Zhang, J.-Y.
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Barrado, D.
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Béjar, V. J. S.
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Bouy, H.
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Burgasser, A.
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Cruz, P.
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Lodieu, N.
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Mas Buitrago, P.
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Phan-Bao, N.
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Solano, E.
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Tata, R.
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Goldman, B.
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Mohandasan, A.
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Reylé, C.
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Smart, R. L.
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Aghanim, N.
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Altieri, B.
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Amara, A.
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Andreon, S.
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Auricchio, N.
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Baccigalupi, C.
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Baldi, M.
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Balestra, A.
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Bardelli, S.
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Battaglia, P.
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Biviano, A.
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Bonchi, A.
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Branchini, E.
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Brescia, M.
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Brinchmann, J.
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Camera, S.
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Cañas-Herrera, G.
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Capobianco, V.
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Carbone, C.
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Carretero, J.
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Casas, S.
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Castellano, M.
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Castignani, G.
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Cavuoti, S.
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Chambers, K. C.
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Cimatti, A.
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Colodro-Conde, C.
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Congedo, G.
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Conselice, C. J.
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Conversi, L.
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Copin, Y.
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Courbin, F.
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Courtois, H. M.
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Cropper, M.
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Cuby, J.-G.
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Da Silva, A.
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Degaudenzi, H.
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De Lucia, G.
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Dolding, C.
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Dole, H.
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Douspis, M.
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Dubath, F.
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Dupac, X.
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Dusini, S.
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Escoffier, S.
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Farina, M.
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Faustini, F.
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Ferriol, S.
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Fotopoulou, S.
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Frailis, M.
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Franceschi, E.
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Galeotta, S.
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George, K.
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Gillis, B.
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Giocoli, C.
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Gómez-Alvarez, P.
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Gracia-Carpio, J.
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Granett, B. R.
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Grazian, A.
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Grupp, F.
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Haugan, S. V. H.
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Hoar, J.
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Holmes, W.
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Hormuth, F.
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Hornstrup, A.
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Jahnke, K.
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Jhabvala, M.
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Keihänen, E.
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Kermiche, S.
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Kiessling, A.
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Kubik, B.
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Kuijken, K.
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Kümmel, M.
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Kunz, M.
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Kurki-Suonio, H.
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Le Boulc'h, Q.
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Le Brun, A. M. C.
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Ligori, S.
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Lilje, P. B.
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Lindholm, V.
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Lloro, I.
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Mainetti, G.
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Maino, D.
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Maiorano, E.
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Mansutti, O.
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Marggraf, O.
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Martinelli, M.
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Martinet, N.
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Marulli, F.
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Massey, R.
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Medinaceli, E.
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Mei, S.
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Mellier, Y.
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Meneghetti, M.
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Merlin, E.
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Meylan, G.
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Mora, A.
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Moresco, M.
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Moscardini, L.
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Nakajima, R.
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Neissner, C.
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Niemi, S.-M.
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Padilla, C.
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Paltani, S.
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Pasian, F.
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Pedersen, K.
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Percival, W. J.
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Pettorino, V.
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Pires, S.
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Polenta, G.
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Poncet, M.
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Popa, L. A.
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Pozzetti, L.
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Raison, F.
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Rebolo, R.
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Renzi, A.
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Rhodes, J.
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Riccio, G.
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Romelli, E.
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Roncarelli, M.
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Saglia, R.
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Sakr, Z.
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Sapone, D.
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Sartoris, B.
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Schewtschenko, J. A.
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Schirmer, M.
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Schneider, P.
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Secroun, A.
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Seidel, G.
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Seiffert, M.
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Serrano, S.
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Simon, P.
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Sirignano, C.
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Sirri, G.
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Stanco, L.
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Steinwagner, J.
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Tallada-Crespí, P.
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Taylor, A. N.
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Tereno, I.
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Toft, S.
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Toledo-Moreo, R.
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Torradeflot, F.
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Tsyganov, A.
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Tutusaus, I.
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Valenziano, L.
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Valiviita, J.
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Vassallo, T.
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Verdoes Kleijn, G.
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Veropalumbo, A.
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Wang, Y.
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Weller, J.
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Zacchei, A.
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Zamorani, G.
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Zerbi, F. M.
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Zucca, E.
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Martín-Fleitas, J.
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Scottez, V.
Abstract
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We present a catalogue of 5306 new ultracool dwarf (UCD) candidates in the three Euclid Deep Fields in the Q1 data release. They range from late M to late T dwarfs, and include 1200 L and T dwarfs. A total of 546 objects have been spectroscopically confirmed, including 329 L dwarfs and 26 T dwarfs. We also provide empirical Euclid colours as a function of spectral type. Our UCD selection criteria are based only on colour (IE − YE > 2.5). The combined requirement for optical detection and a stringent signal-to-noise ratio threshold ensure a high purity of the sample, but at the expense of completeness, especially for T dwarfs. The detections range from magnitudes 19 and 24 in the near-infrared bands, and extend down to 26 in the optical band. We discuss Euclid's capability to identify UCD candidates based on its photometric passbands. The average surface density of detected UCDs on the sky is approximately 100 objects per deg2, including 20 L and T dwarfs per deg2. This leads to an expectation of at least 1.4 million UCDs in the final data release of the Euclid Wide Survey, including at least 300 000 L dwarfs, and more than 2600 T dwarfs, using the strict selection criteria from this work. ★ This paper is published on behalf of the Euclid Consortium.
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