Euclid preparation

Abstract

Euclid is a mission of the European Space Agency that is designed to constrain the properties of dark energy and gravity via weak gravitational lensing and galaxy clustering. It will carry out a wide area imaging and spectroscopy survey (the Euclid Wide Survey: EWS) in visible and near-infrared bands, covering approximately 15 000 deg2 of extragalactic sky in six years. The wide-field telescope and instruments are optimised for pristine point spread function and reduced stray light, producing very crisp images. This paper presents the building of the Euclid reference survey: the sequence of pointings of EWS, deep fields, and calibration fields, as well as spacecraft movements followed by Euclid as it operates in a step-and-stare mode from its orbit around the Lagrange point L2. Each EWS pointing has four dithered frames; we simulated the dither pattern at the pixel level to analyse the effective coverage. We used up-to-date models for the sky background to define the Euclid region-of-interest (RoI). The building of the reference survey is highly constrained from calibration cadences, spacecraft constraints, and background levels; synergies with ground-based coverage were also considered. Via purposely built software, we first generated a schedule for the calibrations and deep fields observations. On a second stage, the RoI was tiled and scheduled with EWS observations, using an algorithm optimised to prioritise the best sky areas, produce a compact coverage, and ensure thermal stability. The result is the optimised reference survey RSD_2021A, which fulfils all constraints and is a good proxy for the final solution. The current EWS covers ≈14 500 deg2. The limiting AB magnitudes (5σ point-like source) achieved in its footprint are estimated to be 26.2 (visible band IE) and 24.5 (for near infrared bands YE, JE, HE); for spectroscopy, the Hα line flux limit is 2 × 10−16 erg−1 cm−2 s−1 at 1600 nm; and for diffuse emission, the surface brightness limits are 29.8 (visible band) and 28.4 (near infrared bands) mag arcsec−2.

The Pan-STARRS1 z > 5.6 Quasar Survey. III. The z ≈ 6 Quasar Luminosity Function

“…Placed in context with the lowerredshift QLF literature (e.g., Richards et al 2006;Croom et al 2009;Glikman et al 2011;Shen & Kelly 2012;Ross et al 2013;Akiyama et al 2018;Schindler et al 2018Schindler et al , 2019Boutsia et al 2021;Pan et al 2022), the recent results underline the (exponential) increase (Schmidt et al 1995;Fan et al 2001a) in quasar activity from z ≈ 6 to its peak at z = 2-3 (Richards et al 2006;Kulkarni et al 2019;Shen et al 2020). The highest-redshift constraint on the QLF at z ≈ 6.7 (Wang et al 2019a) indicates an even more rapid decline of quasar activity at z > 6.5, with consequences for the upcoming quasars surveys at z > 8 (e.g., based on the Euclid mission wide survey; Euclid Collaboration et al 2019; Scaramella et al 2022).…”

Statistics of Galactic-scale Quasar Pairs at Cosmic Noon

“…In order to significantly improve the pair statistics, extend to lower AGN luminosities, and explore the diversity in SMBH and host properties, it is necessary to carry out similar searches with deeper, wide-area surveys at subarcsecond resolution. Upcoming wide-field space missions, such as Euclid (Scaramella et al 2022; to be launched in ∼2023), the Chinese Space Station Telescope (Zhan 2021; to be launched in ∼2024), and the Nancy Grace Roman Space Telescope (Roman, Spergel et al 2015; to be launched before ∼2027), will provide the perfect combination to perform systematic searches of SMBH pairs across cosmic time. All three missions will carry out a wide-field imaging survey in multiple filters with ∼0 05-0 2 resolution and depths of ∼25-28 AB mag, with additional spectroscopic capabilities.…”

Testing Quadratic Maximum Likelihood estimators for forthcoming Stage-IV weak lensing surveys

“…However, we note that this distribution of radii of stars is smaller than the pixel scale for our map resolution, and so a star mask generated using such values as presented in Martinet et al (2021) would give rise to under-sampling in the star mask produced, as all stars would be single pixels, which was found to induce errors in the Pseudo-𝐶 ℓ estimator. Since we are not after an exact realistic distribution of stars in our analysis, we can instead base our star mask on the distribution of 'blinding stars', or avoidance areas, that are expected to be encountered for a space-based observatory (Scaramella et al 2022). These Power spectrum of the sky masks used in our analysis.…”

“…for ground-or space-based cosmic shear surveys (Scaramella et al 2022). Hence, getting this additional area 'for free' by analysing the data through QML methods demonstrates the advantages of using such methods and such investigations into their behaviour for cosmic shear analyses.…”