The Exoplanet Characterization Observatory (
EChO
) is a concept of a dedicated space telescope optimized for low-resolution transit and occultation spectroscopy to study the exoplanet diversity ...through the composition of their atmospheres. The scope of this paper is to answer the following question: Can we schedule a nominal
EChO
mission, with targets known today (in mid 2013), given the science requirements, realistic performances and operational constraints? We examine this issue from the point of view of duration of the mission and the scheduling restrictions with a sample of exoplanet systems known nowadays. We choose different scheduling algorithms taking into account the science and operational constraints and we verified that it is fairly straightforward to schedule a mission scenario over the lifetime of
EChO
compliant with the science requirements. We identified agility as a critical constraint that reduces significantly the efficiency of the survey. We conclude that even with known targets today the
EChO
science objectives can be reached in the 4.5 years duration of the mission. We also show that it is possible to use gaps between exoplanet observations, to fit the required calibration observations, data downlinks and station keeping operations or even to observe more exoplanet targets to be discovered in the coming years.
Euclid preparation Bodendorf, C.; Grupp, F.; Hormuth, F. ...
Astronomy and astrophysics (Berlin),
06/2022, Letnik:
662
Journal Article
Recenzirano
Odprti dostop
Euclid
will be the first space mission to survey most of the extragalactic sky in the 0.95–2.02 µm range, to a 5
σ
point-source median depth of 24.4 AB mag. This unique photometric dataset will find ...wide use beyond
Euclid’s
core science. In this paper, we present accurate computations of the Euclid
Y
E
,
J
E
, and
H
E
passbands used by the Near-Infrared Spectrometer and Photometer (NISP), and the associated photometric system. We pay particular attention to passband variations in the field of view, accounting for, among other factors, spatially variable filter transmission and variations in the angle of incidence on the filter substrate using optical ray tracing. The response curves’ cut-on and cut-off wavelengths – and their variation in the field of view – are determined with ~0.8 nm accuracy, essential for the photometric redshift accuracy required by
Euclid.
After computing the photometric zero points in the AB mag system, we present linear transformations from and to common ground-based near-infrared photometric systems, for normal stars, red and brown dwarfs, and galaxies separately. A
Python
tool to compute accurate magnitudes for arbitrary passbands and spectral energy distributions is provided. We discuss various factors, from space weathering to material outgassing, that may slowly alter
Euclid
’s spectral response. At the absolute flux scale, the
Euclid
in-flight calibration program connects the NISP photometric system to
Hubble
Space Telescope spectrophotometric white dwarf standards; at the relative flux scale, the chromatic evolution of the response is tracked at the milli-mag level. In this way, we establish an accurate photometric system that is fully controlled throughout
Euclid’s
lifetime.
Upcoming surveys will map the growth of large-scale structure with unprecented precision, improving our understanding of the dark sector of the Universe. Unfortunately, much of the cosmological ...information is encoded on small scales, where the clustering of dark matter and the effects of astrophysical feedback processes are not fully understood. This can bias the estimates of cosmological parameters, which we study here for a joint analysis of mock
Euclid
cosmic shear and
Planck
cosmic microwave background data. We use different implementations for the modelling of the signal on small scales and find that they result in significantly different predictions. Moreover, the different non-linear corrections lead to biased parameter estimates, especially when the analysis is extended into the highly non-linear regime, with the Hubble constant,
H
0
, and the clustering amplitude,
σ
8
, affected the most. Improvements in the modelling of non-linear scales will therefore be needed if we are to resolve the current tension with more and better data. For a given prescription for the non-linear power spectrum, using different corrections for baryon physics does not significantly impact the precision of
Euclid
, but neglecting these correction does lead to large biases in the cosmological parameters. In order to extract precise and unbiased constraints on cosmological parameters from
Euclid
cosmic shear data, it is therefore essential to improve the accuracy of the recipes that account for non-linear structure formation, as well as the modelling of the impact of astrophysical processes that redistribute the baryons.
Weak lensing, which is the deflection of light by matter along the line of sight, has proven to be an efficient method for constraining models of structure formation and reveal the nature of dark ...energy. So far, most weak-lensing studies have focused on the shear field that can be measured directly from the ellipticity of background galaxies. However, within the context of forthcoming full-sky weak-lensing surveys such as
Euclid
, convergence maps (mass maps) offer an important advantage over shear fields in terms of cosmological exploitation. While it carry the same information, the lensing signal is more compressed in the convergence maps than in the shear field. This simplifies otherwise computationally expensive analyses, for instance, non-Gaussianity studies. However, the inversion of the non-local shear field requires accurate control of systematic effects caused by holes in the data field, field borders, shape noise, and the fact that the shear is not a direct observable (reduced shear). We present the two mass-inversion methods that are included in the official
Euclid
data-processing pipeline: the standard Kaiser & Squires method (KS), and a new mass-inversion method (KS+) that aims to reduce the information loss during the mass inversion. This new method is based on the KS method and includes corrections for mass-mapping systematic effects. The results of the KS+ method are compared to the original implementation of the KS method in its simplest form, using the
Euclid
Flagship mock galaxy catalogue. In particular, we estimate the quality of the reconstruction by comparing the two-point correlation functions and third- and fourth-order moments obtained from shear and convergence maps, and we analyse each systematic effect independently and simultaneously. We show that the KS+ method substantially reduces the errors on the two-point correlation function and moments compared to the KS method. In particular, we show that the errors introduced by the mass inversion on the two-point correlation of the convergence maps are reduced by a factor of about 5, while the errors on the third- and fourth-order moments are reduced by factors of about 2 and 10, respectively.
Context.
In metric theories of gravity with photon number conservation, the luminosity and angular diameter distances are related via the Etherington relation, also known as the distance duality ...relation (DDR). A violation of this relation would rule out the standard cosmological paradigm and point to the presence of new physics.
Aims.
We quantify the ability of
Euclid
, in combination with contemporary surveys, to improve the current constraints on deviations from the DDR in the redshift range 0 <
z
< 1.6.
Methods.
We start with an analysis of the latest available data, improving previously reported constraints by a factor of 2.5. We then present a detailed analysis of simulated
Euclid
and external data products, using both standard parametric methods (relying on phenomenological descriptions of possible DDR violations) and a machine learning reconstruction using genetic algorithms.
Results.
We find that for parametric methods
Euclid
can (in combination with external probes) improve current constraints by approximately a factor of six, while for non-parametric methods
Euclid
can improve current constraints by a factor of three.
Conclusions.
Our results highlight the importance of surveys like
Euclid
in accurately testing the pillars of the current cosmological paradigm and constraining physics beyond the standard cosmological model.
Euclid preparation Aghanim, N.; Bermejo-Climent, J. R.; Paoletti, D. ...
Astronomy and astrophysics (Berlin),
01/2022, Letnik:
657
Journal Article
Recenzirano
Odprti dostop
The combination and cross-correlation of the upcoming
Euclid
data with cosmic microwave background (CMB) measurements is a source of great expectation since it will provide the largest lever arm of ...epochs, ranging from recombination to structure formation across the entire past light cone. In this work, we present forecasts for the joint analysis of
Euclid
and CMB data on the cosmological parameters of the standard cosmological model and some of its extensions. This work expands and complements the recently published forecasts based on
Euclid
-specific probes, namely galaxy clustering, weak lensing, and their cross-correlation. With some assumptions on the specifications of current and future CMB experiments, the predicted constraints are obtained from both a standard Fisher formalism and a posterior-fitting approach based on actual CMB data. Compared to a
Euclid
-only analysis, the addition of CMB data leads to a substantial impact on constraints for all cosmological parameters of the standard Λ-cold-dark-matter model, with improvements reaching up to a factor of ten. For the parameters of extended models, which include a redshift-dependent dark energy equation of state, non-zero curvature, and a phenomenological modification of gravity, improvements can be of the order of two to three, reaching higher than ten in some cases. The results highlight the crucial importance for cosmological constraints of the combination and cross-correlation of
Euclid
probes with CMB data.
Euclid preparation Moneti, A.; Ilbert, O.; Cuby, J. ...
Astronomy and astrophysics (Berlin),
02/2022, Letnik:
658
Journal Article
Recenzirano
Odprti dostop
We present a new infrared survey covering the three
Euclid
deep fields and four other
Euclid
calibration fields using
Spitzer
Space Telescope’s Infrared Array Camera (IRAC). We combined these new ...observations with all relevant IRAC archival data of these fields in order to produce the deepest possible mosaics of these regions. In total, these observations represent nearly 11 % of the total
Spitzer
Space Telescope mission time. The resulting mosaics cover a total of approximately 71.5 deg
2
in the 3.6 and 4.5 μm bands, and approximately 21.8 deg
2
in the 5.8 and 8 μm bands. They reach at least 24 AB magnitude (measured to 5
σ
, in a 2″.5 aperture) in the 3.6 μm band and up to ∼5 mag deeper in the deepest regions. The astrometry is tied to the
Gaia
astrometric reference system, and the typical astrometric uncertainty for sources with 16 < 3.6< 19 is ≲0″.15. The photometric calibration is in excellent agreement with previous WISE measurements. We extracted source number counts from the 3.6 μm band mosaics, and they are in excellent agreement with previous measurements. Given that the
Spitzer
Space Telescope has now been decommissioned, these mosaics are likely to be the definitive reduction of these IRAC data. This survey therefore represents an essential first step in assembling multi-wavelength data on the
Euclid
deep fields, which are set to become some of the premier fields for extragalactic astronomy in the 2020s.
Context.
Future weak lensing surveys, such as the
Euclid
mission, will attempt to measure the shapes of billions of galaxies in order to derive cosmological information. These surveys will attain ...very low levels of statistical error, and systematic errors must be extremely well controlled. In particular, the point spread function (PSF) must be estimated using stars in the field, and recovered with high accuracy.
Aims.
The aims of this paper are twofold. Firstly, we took steps toward a nonparametric method to address the issue of recovering the PSF field, namely that of finding the correct PSF at the position of any galaxy in the field, applicable to
Euclid
. Our approach relies solely on the data, as opposed to parametric methods that make use of our knowledge of the instrument. Secondly, we studied the impact of imperfect PSF models on the shape measurement of galaxies themselves, and whether common assumptions about this impact hold true in an
Euclid
scenario.
Methods.
We extended the recently proposed resolved components analysis approach, which performs super-resolution on a field of under-sampled observations of a spatially varying, image-valued function. We added a spatial interpolation component to the method, making it a true 2-dimensional PSF model. We compared our approach to
PSFEx
, then quantified the impact of PSF recovery errors on galaxy shape measurements through image simulations.
Results.
Our approach yields an improvement over
PSFEx
in terms of the PSF model and on observed galaxy shape errors, though it is at present far from reaching the required
Euclid
accuracy. We also find that the usual formalism used for the propagation of PSF model errors to weak lensing quantities no longer holds in the case of an
Euclid
-like PSF. In particular, different shape measurement approaches can react differently to the same PSF modeling errors.
Euclid preparation Gómez-Alvarez, P.; Altieri, B.; Laureijs, R. ...
Astronomy and astrophysics (Berlin),
01/2022, Letnik:
657
Journal Article
Recenzirano
Odprti dostop
Context.
While
Euclid
is an ESA mission specifically designed to investigate the nature of dark energy and dark matter, the planned unprecedented combination of survey area (∼15 000 deg
2
), spatial ...resolution, low sky-background, and depth also make
Euclid
an excellent space observatory for the study of the low surface brightness Universe. Scientific exploitation of the extended low surface brightness structures requires dedicated calibration procedures that are yet to be tested.
Aims.
We investigate the capabilities of
Euclid
to detect extended low surface brightness structure by identifying and quantifying sky-background sources and stray-light contamination. We test the feasibility of generating sky flat-fields to reduce large-scale residual gradients in order to reveal the extended emission of galaxies observed in the
Euclid
survey.
Methods.
We simulated a realistic set of
Euclid
/VIS observations, taking into account both instrumental and astronomical sources of contamination, including cosmic rays, stray-light, zodiacal light, interstellar medium, and the cosmic infrared background, while simulating the effects of background sources in the field of view.
Results.
We demonstrate that a combination of calibration lamps, sky flats, and self-calibration would enable recovery of emission at a limiting surface brightness magnitude of
μ
lim
= 29.5
−0.27
+0.08
mag arcsec
−2
(3
σ
, 10 × 10 arcsec
2
) in the Wide Survey, and it would reach regions deeper by 2 mag in the Deep Surveys.
Conclusions.Euclid
/VIS has the potential to be an excellent low surface brightness observatory. Covering the gap between pixel-to-pixel calibration lamp flats and self-calibration observations for large scales, the application of sky flat-fielding will enhance the sensitivity of the VIS detector at scales larger than 1″, up to the size of the field of view, enabling
Euclid
to detect extended surface brightness structures below
μ
lim
= 31 mag arcsec
−2
and beyond.
Context.
The data from the
Euclid
mission will enable the measurement of the angular positions and weak lensing shapes of over a billion galaxies, with their photometric redshifts obtained together ...with ground-based observations. This large dataset, with well-controlled systematic effects, will allow for cosmological analyses using the angular clustering of galaxies (GC
ph
) and cosmic shear (WL). For
Euclid
, these two cosmological probes will not be independent because they will probe the same volume of the Universe. The cross-correlation (XC) between these probes can tighten constraints and is therefore important to quantify their impact for
Euclid
.
Aims.
In this study, we therefore extend the recently published
Euclid
forecasts by carefully quantifying the impact of XC not only on the final parameter constraints for different cosmological models, but also on the nuisance parameters. In particular, we aim to decipher the amount of additional information that XC can provide for parameters encoding systematic effects, such as galaxy bias, intrinsic alignments (IAs), and knowledge of the redshift distributions.
Methods.
We follow the Fisher matrix formalism and make use of previously validated codes. We also investigate a different galaxy bias model, which was obtained from the Flagship simulation, and additional photometric-redshift uncertainties; we also elucidate the impact of including the XC terms on constraining these latter.
Results.
Starting with a baseline model, we show that the XC terms reduce the uncertainties on galaxy bias by ∼17% and the uncertainties on IA by a factor of about four. The XC terms also help in constraining the
γ
parameter for minimal modified gravity models. Concerning galaxy bias, we observe that the role of the XC terms on the final parameter constraints is qualitatively the same irrespective of the specific galaxy-bias model used. For IA, we show that the XC terms can help in distinguishing between different models, and that if IA terms are neglected then this can lead to significant biases on the cosmological parameters. Finally, we show that the XC terms can lead to a better determination of the mean of the photometric galaxy distributions.
Conclusions.
We find that the XC between GC
ph
and WL within the
Euclid
survey is necessary to extract the full information content from the data in future analyses. These terms help in better constraining the cosmological model, and also lead to a better understanding of the systematic effects that contaminate these probes. Furthermore, we find that XC significantly helps in constraining the mean of the photometric-redshift distributions, but, at the same time, it requires more precise knowledge of this mean with respect to single probes in order not to degrade the final “figure of merit”.
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