June
2026
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2026A&A...711A..25E
Authors
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Euclid Collaboration
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Allen, N.
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Oesch, P. A.
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Bowler, R. A. A.
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Toft, S.
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Matharu, J.
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Weaver, J. R.
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McPartland, C. J. R.
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Shuntov, M.
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Sanders, D. B.
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Mobasher, B.
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McCracken, H. J.
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Atek, H.
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Bañados, E.
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Barrow, S. W. J.
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Belladitta, S.
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Carollo, D.
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Castellano, M.
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Conselice, C. J.
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Eisenhardt, P. R. M.
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Harikane, Y.
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Murphree, G.
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Stefanon, M.
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Wilkins, S. M.
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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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Bender, R.
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Biviano, 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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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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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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Da Silva, A.
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Degaudenzi, H.
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De Lucia, G.
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Dole, H.
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Dubath, F.
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Duncan, C. A. J.
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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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Farinelli, R.
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Faustini, F.
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Ferriol, S.
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Finelli, F.
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Fourmanoit, N.
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Frailis, M.
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Franceschi, E.
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Fumana, M.
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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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Gracia-Carpio, J.
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Grazian, A.
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Grupp, F.
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Haugan, S. V. H.
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Hoekstra, H.
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Holmes, W.
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Hook, I. M.
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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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Joachimi, B.
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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 Brun, A. M. C.
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Le Mignant, D.
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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. J.
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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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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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Schirmer, M.
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Schneider, P.
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Schrabback, T.
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Secroun, A.
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Sefusatti, E.
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Seidel, G.
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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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Teplitz, H. I.
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Tereno, I.
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Tessore, N.
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Toledo-Moreo, R.
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Torradeflot, F.
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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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Wang, Y.
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Weller, J.
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Zamorani, G.
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Zerbi, F. M.
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Zucca, E.
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Allevato, V.
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Ballardini, M.
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Bolzonella, M.
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Bozzo, E.
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Burigana, C.
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Cabanac, R.
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Calabrese, M.
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Cappi, A.
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Di Ferdinando, D.
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Escartin Vigo, J. A.
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Gabarra, L.
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Hartley, W. G.
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Maoli, R.
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Martín-Fleitas, J.
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Matthew, S.
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Maturi, M.
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Mauri, N.
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Metcalf, R. B.
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Pezzotta, A.
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Pöntinen, M.
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Porciani, C.
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Risso, I.
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Scottez, V.
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Sereno, M.
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Tenti, M.
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Viel, M.
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Wiesmann, M.
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Akrami, Y.
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Andika, I. T.
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Anselmi, S.
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Archidiacono, M.
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Atrio-Barandela, F.
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Bertacca, D.
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Bethermin, M.
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Blanchard, A.
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Blot, L.
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Bonici, M.
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Brown, M. L.
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Bruton, S.
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Calabro, A.
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Camacho Quevedo, B.
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Caro, F.
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Carvalho, C. S.
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Castro, T.
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Cogato, F.
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Conseil, S.
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Contini, T.
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Cooray, A. R.
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Cucciati, O.
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Desprez, G.
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Díaz-Sánchez, A.
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Diaz, J. J.
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Di Domizio, S.
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Diego, J. M.
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Elkhashab, M. Y.
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Enia, A.
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Fang, Y.
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Ferrari, A. G.
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Finoguenov, A.
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Fontana, A.
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Fontanot, F.
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Franco, A.
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Ganga, K.
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García-Bellido, J.
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Gasparetto, T.
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Gautard, V.
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Gaztanaga, E.
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Giacomini, F.
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Gianotti, F.
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Gozaliasl, G.
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Guidi, M.
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Gutierrez, C. M.
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Hall, A.
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Hemmati, S.
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Hernández-Monteagudo, C.
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Hildebrandt, H.
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Hjorth, J.
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Kajava, J. J. E.
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Kang, Y.
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Kansal, V.
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Karagiannis, D.
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Kiiveri, K.
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Kim, J.
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Kirkpatrick, C. C.
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Kruk, S.
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Legrand, L.
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Lembo, M.
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Lepori, F.
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Leroy, G.
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Lesci, G. F.
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Lesgourgues, J.
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Liaudat, T. I.
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Liu, S. J.
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Lopez Lopez, X.
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Macias-Perez, J.
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Magliocchetti, M.
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Mannucci, F.
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Martins, C. J. A. P.
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Maurin, L.
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Miluzio, M.
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Monaco, P.
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Moretti, C.
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Morgante, G.
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Naidoo, K.
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Navarro-Alsina, A.
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Nesseris, S.
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Paoletti, D.
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Passalacqua, F.
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Paterson, K.
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Patrizii, L.
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Pello, R.
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Pisani, A.
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Potter, D.
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Quai, S.
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Radovich, M.
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Rocci, P.-F.
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Rodighiero, G.
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Sacquegna, S.
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Sahlén, M.
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Sarpa, E.
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Schneider, A.
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Schultheis, M.
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Sciotti, D.
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Sellentin, E.
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Shankar, F.
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Smith, L. C.
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Sorce, J. G.
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Tanidis, K.
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Tao, C.
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Testera, G.
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Teyssier, R.
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Tosi, S.
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Troja, A.
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Tucci, M.
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Valieri, C.
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Venhola, A.
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Vergani, D.
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Verza, G.
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Vielzeuf, P.
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Walton, N. A.
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Scott, D.
Abstract
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The evolution of the rest-frame ultraviolet luminosity function (UV LF) is a powerful probe of early star formation and galaxy stellar mass build-up. At z > 6, its bright end (MUV < −21) remains poorly constrained due to small survey volumes of existing near-infrared (NIR) space-based imaging surveys. The Euclid Deep Fields (EDFs) will cover 53 deg2 with NIR coverage down to a magnitude of 26.5 AB, providing a factor of 100 increase in area compared to previous space-based surveys. They thus offer an unprecedented opportunity to select bright z > 6 Lyman break galaxies (LBGs) and definitively constrain the bright end of the UV LF. With its NIR coverage extending to ∼2 μm, Euclid has the power to detect galaxies out to z ∼ 13. Here, we present a forecast for the number densities of z > 6 galaxies that Euclid is expected to observe in the final EDF dataset. Using synthetic photometry from spectral energy distribution (SED) templates of z = 5─15 galaxies, z = 1─4 interlopers, and Milky Way M-, L-, and T-type dwarfs, we investigate optimal selection methodologies for high-z LBGs in the EDF datasets. We find that a combination of signal-to-noise ratio (S/N) cuts with SED fitting (over optical to MIR bands) yields the highest fidelity sample, recovering more than 76% of the input synthetic z > 6 LBGs, while limiting low-z contamination to less than 10%. This contamination does not include effects from instrumental artefacts, which will impact the first Euclid data releases. Auxiliary data prove critical: optical coverage from the Hyper Suprime Camera and Vera C. Rubin Observatory will distinguish genuine Lyman breaks from contaminant features, while Spitzer Space Telescope/IRAC data are vital for recovering z > 10 sources. Based on empirical double power-law LF models, we expect more than 100 000 LBGs at z = 6─12 and more than 100 sources as far back as z > 12 in the final Euclid data release. In contrast, the steeper Schechter LF models predict no detections of z > 12 LBGs. In this work, we also present two ultra-luminous (MUV < −23.5) candidates selected from the Q1 EDF-N dataset (Euclid Quick Data Release). If their redshifts are reliable, their magnitudes suggest a DPL UV LF model at z > 9. This highlights the power of Euclid in constraining the bright end of the UV LF in the early Universe and in identifying the most luminous sources that are valuable for further follow-up observations.
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