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- Title
Euclid preparation: V. Predicted yield of redshift 7 < z < 9 quasars from the wide survey.
- Authors
Euclid Collaboration; Barnett, R.; Warren, S. J.; Mortlock, D. J.; Cuby, J.-G.; Conselice, C.; Hewett, P. C.; Willott, C. J.; Auricchio, N.; Balaguera-Antolínez, A.; Baldi, M.; Bardelli, S.; Bellagamba, F.; Bender, R.; Biviano, A.; Bonino, D.; Bozzo, E.; Branchini, E.; Brescia, M.; Brinchmann, J.
- Abstract
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 EuclidOYJH 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.
- Subjects
EUCLID; QUASARS; PHOTOMETRY; GALAXIES; LUMINOSITY; WAVELENGTHS; COLOR
- Publication
Astronomy & Astrophysics / Astronomie et Astrophysique, 2019, Vol 631, p1
- ISSN
0004-6361
- Publication type
Article
- DOI
10.1051/0004-6361/201936427