November
2019
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2019A&A...631A..85E
Authors
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Euclid Collaboration
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Barnett, R.
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Warren, S. J.
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Mortlock, D. J.
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Cuby, J. -G.
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Conselice, C.
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Hewett, P. C.
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Willott, C. J.
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Auricchio, N.
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Balaguera-Antolínez, A.
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Baldi, M.
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Bardelli, S.
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Bellagamba, F.
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Bender, R.
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Biviano, A.
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Bonino, D.
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Bozzo, E.
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Branchini, E.
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Brescia, M.
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Brinchmann, J.
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Burigana, C.
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Camera, S.
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Capobianco, V.
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Carbone, C.
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Carretero, J.
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Carvalho, C. S.
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Castander, F. J.
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Castellano, M.
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Cavuoti, S.
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Cimatti, A.
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Clédassou, R.
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Congedo, G.
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Conversi, L.
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Copin, Y.
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Corcione, L.
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Coupon, J.
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Courtois, H. M.
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Cropper, M.
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Da Silva, A.
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Duncan, C. A. J.
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Dusini, S.
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Ealet, A.
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Farrens, S.
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Fosalba, P.
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Fotopoulou, S.
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Fourmanoit, N.
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Frailis, M.
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Fumana, M.
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Galeotta, S.
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Garilli, B.
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Gillard, W.
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Gillis, B. R.
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Graciá-Carpio, J.
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Grupp, F.
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Hoekstra, H.
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Hormuth, F.
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Israel, H.
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Jahnke, K.
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Kermiche, S.
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Kilbinger, M.
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Kirkpatrick, C. C.
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Kitching, T.
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Kohley, R.
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Kubik, B.
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Kunz, M.
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Kurki-Suonio, H.
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Laureijs, R.
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Ligori, S.
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Lilje, P. B.
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Lloro, I.
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Maiorano, E.
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Mansutti, O.
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Marggraf, O.
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Martinet, N.
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Marulli, F.
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Massey, R.
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Mauri, N.
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Medinaceli, E.
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Mei, S.
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Mellier, Y.
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Metcalf, R. B.
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Metge, J. J.
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Meylan, G.
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Moresco, M.
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Moscardini, L.
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Munari, E.
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Neissner, C.
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Niemi, S. M.
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Nutma, T.
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Padilla, C.
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Paltani, S.
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Pasian, F.
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Paykari, P.
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Percival, W. J.
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Pettorino, V.
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Polenta, G.
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Poncet, M.
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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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Rix, H. -W.
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Romelli, E.
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Roncarelli, M.
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Rossetti, E.
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Saglia, R.
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Sapone, D.
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Scaramella, R.
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Schneider, P.
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Scottez, V.
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Secroun, A.
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Serrano, S.
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Sirri, G.
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Stanco, L.
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Sureau, F.
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Tallada-Crespí, P.
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Tavagnacco, D.
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Taylor, A. N.
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Tenti, M.
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Tereno, I.
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Toledo-Moreo, R.
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Torradeflot, F.
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Valenziano, L.
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Vassallo, T.
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Wang, Y.
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Zacchei, A.
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Zamorani, G.
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Zoubian, J.
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Zucca, E.
Abstract
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We provide predictions of the yield of 7 < z < 9 quasars from the Euclid wide survey, updating the calculation presented in the Euclid Red Book in several ways. We account for revisions to the Euclid near-infrared filter wavelengths; we adopt steeper rates of decline of the quasar luminosity function (QLF; Φ) with redshift, Φ ∝ 10k(z - 6), k = -0.72, and a further steeper rate of decline, k = -0.92; we use better models of the contaminating populations (MLT dwarfs and compact early-type galaxies); and we make use of an improved Bayesian selection method, compared to the colour cuts used for the Red Book calculation, allowing the identification of fainter quasars, down to JAB ∼ 23. Quasars at z > 8 may be selected from Euclid OYJH photometry alone, but selection over the redshift interval 7 < z < 8 is greatly improved by the addition of z-band data from, e.g., Pan-STARRS and LSST. We calculate predicted quasar yields for the assumed values of the rate of decline of the QLF beyond z = 6. If the decline of the QLF accelerates beyond z = 6, with k = -0.92, Euclid should nevertheless find over 100 quasars with 7.0 < z < 7.5, and ∼25 quasars beyond the current record of z = 7.5, including ∼8 beyond z = 8.0. The first Euclid quasars at z > 7.5 should be found in the DR1 data release, expected in 2024. It will be possible to determine the bright-end slope of the QLF, 7 < z < 8, M1450 < -25, using 8 m class telescopes to confirm candidates, but follow-up with JWST or E-ELT will be required to measure the faint-end slope. Contamination of the candidate lists is predicted to be modest even at JAB ∼ 23. The precision with which k can be determined over 7 < z < 8 depends on the value of k, but assuming k = -0.72 it can be measured to a 1σ uncertainty of 0.07.
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