Euclid preparation

R. Barnett , S. J. Warren , D. J. Mortlock , J.-G. Cuby (1) , C. Conselice , P. C. Hewett , C. J. Willott , N. Auricchio , A. Balaguera-Antolínez , M. Baldi , S. Bardelli , F. Bellagamba , R. Bender , A. Biviano (2) , D. Bonino , E. Bozzo , E. Branchini (3) , M. Brescia , J. Brinchmann , C. Burigana , S. Camera , V. Capobianco , C. Carbone (4) , J. Carretero , C. S. Carvalho (5, 6) , F. J. Castander , M. Castellano , S. Cavuoti , A. Cimatti (7) , R. Clédassou (8) , G. Congedo , L. Conversi , Y. Copin (9) , L. Corcione , J. Coupon , H. M. Courtois (9) , M. Cropper (10) , A. da Silva , C. A. J. Duncan , S. Dusini , A. Ealet (11, 9) , S. Farrens (12) , P. Fosalba , S. Fotopoulou , N. Fourmanoit (11) , M. Frailis , M. Fumana , S. Galeotta , B. Garilli (13) , W. Gillard (11) , B. R. Gillis (14) , J. Graciá-Carpio (15) , F. Grupp , H. Hoekstra , F. Hormuth , H. Israel , K. Jahnke , S. Kermiche (11) , M. Kilbinger (16) , C. C. Kirkpatrick (17) , T. Kitching , R. Kohley , B. Kubik (18) , M. Kunz , H. Kurki-Suonio (19) , R. Laureijs , S. Ligori , P. B. Lilje , I. Lloro , E. Maiorano , O. Mansutti , O. Marggraf , N. Martinet (20) , F. Marulli (21) , R. Massey , N. Mauri , E. Medinaceli , S. Mei (22) , Y. Mellier (23) , R. B. Metcalf , J. J. Metge (8) , G. Meylan , M. Moresco (24) , L. Moscardini , E. Munari , C. Neissner , S. M. Niemi , T. Nutma , C. Padilla , S. Paltani , F. Pasian , P. Paykari (10) , W. J. Percival (25) , V. Pettorino (26) , G. Polenta (27) , M. Poncet (8) , L. Pozzetti (28) , F. Raison , A. Renzi , J. Rhodes , H.-W. Rix , E. Romelli , M. Roncarelli , E. Rossetti (29) , R. Saglia , D. Sapone , R. Scaramella , P. Schneider (30) , V. Scottez (31) , A. Secroun (11) , S. Serrano , G. Sirri , L. Stanco , F. Sureau (26) , P. Tallada-Crespí , D. Tavagnacco (2) , A. N. Taylor (32) , M. Tenti , I. Tereno , R. Toledo-Moreo , F. Torradeflot , L. Valenziano (33) , T. Vassallo (34) , Y. Wang (35) , A. Zacchei , G. Zamorani , J. Zoubian (11) , E. Zucca (36)

1 AMU - Aix Marseille Université
2 OAT - INAF - Osservatorio Astronomico di Trieste
3 DF-Roma3 - Dipartimento de Fisica Roma Tre
4 CNR - Consiglio Nazionale delle Ricerche [Bologna]
5 I2BC - Institut de Biologie Intégrative de la Cellule
6 SEN - Sénescence et stabilité génomique
7 Dipartimento di Astronomia
8 CNES - Centre National d'Études Spatiales [Toulouse]
9 IP2I Lyon - Institut de Physique des 2 Infinis de Lyon
10 MSSL - Mullard Space Science Laboratory
11 CPPM - Centre de Physique des Particules de Marseille
12 IRFU - Institut de Recherches sur les lois Fondamentales de l'Univers
13 IASF-MI - Istituto di Astrofisica Spaziale e Fisica Cosmica - Milano
14 ROE - Royal Observatory Edinburgh
15 MPE - Max Planck Institute for Extraterrestrial Physics
16 DAP - Département d'Astrophysique (ex SAP)
17 Department of Physics [Helsinki]
18 IPNL - Institut de Physique Nucléaire de Lyon
19 Helsingin yliopisto = Helsingfors universitet = University of Helsinki
20 LAM - Laboratoire d'Astrophysique de Marseille
21 UNIBO - Alma Mater Studiorum Università di Bologna [Bologna]
22 LERMA (UMR_8112) - Laboratoire d'Etude du Rayonnement et de la Matière en Astrophysique et Atmosphères
23 IAP - Institut d'Astrophysique de Paris
24 Dipartimento di Fisica e Astronomia [Bologna]
25 University of Waterloo [Waterloo]
26 AIM (UMR_7158 / UMR_E_9005 / UM_112) - Astrophysique Interprétation Modélisation
27 Università degli Studi di Roma Tor Vergata [Roma]
28 OABO - INAF - Osservatorio Astronomico di Bologna
29 DSA3 - Department of Agricultural, Food and Environmental Sciences, University of Perugia
30 Department of Biochemistry [Lausanne]
31 IAP - Institut d'Astrophysique de Paris
32 DEMR, ONERA, Université Paris Saclay (COmUE) [Palaiseau]
33 ARENA - Antarctic Research a European Network for Astrophysics
34 BMBI - Biomécanique et Bioingénierie
35 Continental Dynamics Laboratory [CAGS Beijing]
36 Oncology Institute of Southern Switzerland

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; $\Phi$) with redshift, $\Phi$ ∝ 10$^{k(z−6)}$, $k$ = −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 $J_{AB}$ $\sim$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 $\sim$25 quasars beyond the current record of z = 7.5, including $\sim$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, $M_{1450}$ <  −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 $J_{AB}$$\sim$ 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 1$\sigma$ uncertainty of 0.07.

Keywords: surveys; quasars: general; methods: statistical

Domains: Physics [physics]; Astrophysics [astro-ph]

R. Barnett, S. J. Warren, D. J. Mortlock, J.-G. Cuby, C. Conselice, et al.. Euclid preparation: V. Predicted yield of redshift 7 < z < 9 quasars from the wide survey. Astronomy and Astrophysics - A&A, 2019, 631, pp.A85. ⟨10.1051/0004-6361/201936427⟩. ⟨cea-02334278⟩