91̽»¨

Abstract:

The intracluster light (ICL) permeating galaxy clusters is a tracer of the cluster assembly history and potentially a tracer of their dark matter structure. In this work, we explore the capability of the Euclid Wide Survey to detect ICL using HE-band mock images. We simulated clusters across a range of redshifts (0.3-1.8) and halo masses (1013:9-1015:0 M_) using an observationally motivated model of ICL. We identified a 50- 200 kpc circular annulus around the brightest cluster galaxy (BCG) in which the signal-to-noise ratio of the ICL is maximised and used the S/N within this aperture as our figure of merit for ICL detection.We compared three state-of-the-art methods for ICL detection and found that a method that performs simple aperture photometry after high-surface brightness source masking is able to detect ICL with minimal bias for clusters more massive than 1014:2 M_. The S/N of the ICL detection is primarily limited by the redshift of the cluster, which is driven by cosmological dimming rather than the mass of the cluster. Assuming the ICL in each cluster contains 15% of the stellar light, we forecast that Euclid will be able to measure the presence of ICL in up to _80 000 clusters of >1014:2 M_ between z = 0:3 and 1.5 with an S/N > 3. Half of these clusters will reside below z = 0:75, and the majority of those below z = 0:6 will be detected with an S/N > 20. A few thousand clusters at 1:3 < z < 1:5 will have ICL detectable with an S/N > 3. The surface brightness profile of the ICL model is strongly dependent on both the mass of the cluster and the redshift at which it is observed so that the outer ICL is best observed in the most massive clusters of >1014:7 M_. Euclid will detect the ICL at a distance of more than 500 kpc from the BCG, up to z = 0:7, in several hundred of these massive clusters over its large survey volume.

Abstract:

<jats:p><jats:italic>Context.</jats:italic> Current and future large-scale structure surveys aim to constrain the neutrino mass and the equation of state of dark energy. To do this efficiently, rapid yet accurate evaluation of the matter power spectrum in the presence of these effects is essential.</jats:p> <jats:p><jats:italic>Aims.</jats:italic> We aim to construct accurate and interpretable symbolic approximations of the linear and nonlinear matter power spectra as a function of cosmological parameters in extended ΛCDM models that contain massive neutrinos and nonconstant equations of state for dark energy. This constitutes an extension of the S<jats:sc>YREN-HALOFIT</jats:sc> emulators to incorporate these two effects, which we call S<jats:sc>YREN-NEW</jats:sc> (SYmbolic-Regression-ENhanced power spectrum emulator with NEutrinos and <jats:italic>W</jats:italic><jats:sub>0</jats:sub>−<jats:italic>w</jats:italic><jats:sub><jats:italic>a</jats:italic></jats:sub>). We also wish to obtain a simple approximation of the derived parameter, <jats:italic>σ</jats:italic><jats:sub>8</jats:sub>, as a function of the cosmological parameters for these models.</jats:p> <jats:p><jats:italic>Methods.</jats:italic> We utilizedd symbolic regression to efficiently search through candidate analytic expressions to approximate the various quantities of interest. Our results for the linear power spectrum are designed to emulate C<jats:sc>LASS</jats:sc>, whereas for the nonlinear case we aim to match the results of E<jats:sc>UCLIDEMULATOR</jats:sc>2. We compared our results to existing emulators and <jats:italic>N</jats:italic>-body simulations.</jats:p> <jats:p><jats:italic>Results.</jats:italic> Our analytic emulators for <jats:italic>σ</jats:italic><jats:sub>8</jats:sub>, and the linear and nonlinear power spectra achieve root mean squared errors of 0.1%, 0.3%, and 1.3%, respectively, across a wide range of cosmological parameters, redshifts and wavenumbers. The error on the nonlinear power spectrum is reduced by approximately a factor of 2 when considering observationally plausible dark energy models and neutrino masses. We verify that emulator-related discrepancies are subdominant compared to observational errors and other modeling uncertainties when computing shear power spectra for LSST-like surveys. Our expressions have similar accuracy to existing (numerical) emulators, but are at least an order of magnitude faster, both on a CPU and a GPU.</jats:p> <jats:p><jats:italic>Conclusions.</jats:italic> Our work greatly improves the accuracy, speed, and applicability range of current symbolic approximations of the linear and nonlinear matter power spectra. These now cover the same range of cosmological models as many numerical emulators with similar accuracy, but are much faster and more interpretable. We provide publicly available code for all symbolic approximations found.</jats:p>

Abstract:

The recent evidence for dynamical dark energy from DESI, in combination with other cosmological data, has generated significant interest in understanding the nature of dark energy and its underlying microphysics. However, interpreting these results critically depends on how dark energy is parameterized. This paper examines the robustness of conclusions about the viability of particular kinds of dynamical dark energy models to the choice of parameterization, focusing on four popular two-parameter families: the Chevallier-Polarski-Linder (CPL), Jassal-Bagla-Padmanabhan (JBP), Barboza-Alcaniz (BA), and exponential (EXP) parameterizations. We find that conclusions regarding the viability of minimally and non-minimally coupled quintessence models are independent of the parameterization adopted. We demonstrate this both by mapping these dark energy models into the (w 0, wa ) parameter space defined by these various parameterizations and by showing that all of these parameterizations can equivalently account for the phenomenology predicted by these dark energy models to a high degree of accuracy.

Abstract:

This paper presents the specification, design, and development of the Visible Camera (VIS) on the European Space Agency’s Euclid mission. VIS is a large optical-band imager with a field of view of 0.54 deg2 sampled at 000 . 1 with an array of 609 Megapixels and a spatial resolution of 000 . 18. It will be used to survey approximately 14 000 deg2 of extragalactic sky to measure the distortion of galaxies in the redshift range z = 0.1–1.5 resulting from weak gravitational lensing, one of the two principal cosmology probes leveraged by Euclid. With photometric redshifts, the distribution of dark matter can be mapped in three dimensions, and the extent to which this has changed with look-back time can be used to constrain the nature of dark energy and theories of gravity. The entire VIS focal plane will be transmitted to provide the largest images of the Universe from space to date, specified to reach mAB ≥ 24.5 with a signal-to-noise ratio S/N ≥ 10 in a single broad IE ≃ (r + i + z) band over a six-year survey. The particularly challenging aspects of the instrument are the control and calibration of observational biases, which lead to stringent performance requirements and calibration regimes. With its combination of spatial resolution, calibration knowledge, depth, and area covering most of the extra-Galactic sky, VIS will also provide a legacy data set for many other fields. This paper discusses the rationale behind the conception of VIS and describes the instrument design and development, before reporting the prelaunch performance derived from ground calibrations and brief results from the in-orbit commissioning. VIS should reach fainter than mAB = 25 with S/N ≥ 10 for galaxies with a full width at half maximum of 000 . 3 in a 100 . 3 diameter aperture over the Wide Survey, and mAB ≥ 26.4 for a Deep Survey that will cover more than 50 deg2. The paper also describes how the instrument works with the Euclid telescope and survey, and with the science data processing, to extract the cosmological information.