July
2026
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2026A&A...711A.104Y
Authors
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Yang, D.
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Hennawi, J. F.
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Guarneri, F.
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Wolf, J.
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Belladitta, S.
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Schindler, J.-T.
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Hughes, A. C. N.
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Bañados, E.
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Mortlock, D. J.
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Yang, J.
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Wang, F.
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Fan, X.
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Jahnke, K.
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Stern, D.
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Willott, C. J.
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Barth, A. J.
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Rottgering, H. J. A.
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Varadaraj, R. G.
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Decarli, R.
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Eilers, A.-C.
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Ezziati, M.
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Fu, Y.
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Huang, J.
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Jin, X.
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Kang, Y.
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Martinez-Ramirez, L. N.
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Matsuoka, Y.
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Onoue, M.
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Pello, R.
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Remigio, R. P.
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Tee, W. L.
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Venemans, B.
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Vietri, G.
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Wang, B.
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Abbo, L. J.
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Atek, H.
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Bisogni, S.
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Bosman, S. E. I.
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Bowler, R. A. A.
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Conselice, C. J.
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Davies, F. B.
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Gutierrez, C. M.
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Harikane, Y.
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Rubinur, K.
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Lovell, C. C.
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Magliocchetti, M.
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Matthee, J.
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Ricci, F.
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Scialpi, M.
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Scott, D.
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Spinoglio, L.
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Tarsitano, F.
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Toba, Y.
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Walter, F.
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Weaver, J. R.
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Zamorani, G.
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Altieri, B.
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Amara, A.
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Andreon, S.
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Aussel, H.
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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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Branchini, E.
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Brescia, M.
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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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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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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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Cuillandre, J.-C.
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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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Farinelli, R.
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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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Gómez-Alvarez, P.
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Gracia-Carpio, J.
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Grazian, A.
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Grupp, F.
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Guzzo, L.
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Gwyn, S.
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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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Jhabvala, M.
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Kermiche, S.
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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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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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McCracken, H. 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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Mohr, J. J.
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Mora, A.
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Moresco, M.
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Moscardini, L.
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Munari, E.
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Nakajima, R.
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Neissner, C.
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Nichol, R. 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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Racca, G. D.
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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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Rix, H.-W.
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Romelli, E.
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Roncarelli, M.
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Rosset, C.
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Rusholme, B.
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Saglia, R.
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Sakr, Z.
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Sapone, D.
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Sauvage, M.
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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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Seidel, G.
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Serrano, S.
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Sihvola, E.
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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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Tereno, I.
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Tessore, N.
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Toft, S.
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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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Zerbi, F. M.
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Zucca, E.
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Fabbian, G.
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Huertas-Company, M.
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Martín-Fleitas, J.
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Monaco, P.
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Scottez, V.
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Viel, M.
Abstract
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We report the discovery of 31 new high-z quasars in the redshift range 6.6 < z < 7.8. These quasars were selected from approximately 3000 deg2 of sky covered during the first 1.5 years of the Euclid Wide Survey, representing the initial results of the Euclid high-z quasar search. Our candidate selection employed multiple machine-learning and probabilistic techniques applied to the EuclidIE, YE, JE, and HE images, supplemented by ancillary z-band data when available. Spectroscopic follow-up observations were carried out with Keck, Magellan, and the Large Binocular Telescope (LBT). Among the new discoveries, there are 12 quasars at z ≥ 7, more than doubling the number of previously known quasars at z ≥ 7. The newly discovered quasars exhibit 21.2 < JE < 23.2 (−25.5 < M1450 < −23.6), extending quasar studies to the faint end of the quasar luminosity function (QLF) at z ≳ 7. The quasar with the highest-z, EUCL J172902.75+641018.1 at z ≍ 7.77, sets the new redshift record for the most distant quasar ever reported. These discoveries demonstrate Euclid's transformative role in high-z quasar discovery and set the stage for future follow-up studies of the early galaxies hosting quasars, supermassive black hole growth, and the intergalactic medium in the epoch of reionisation. ★ This paper is published on behalf of the Euclid Consortium.
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