Euclid preparation Blanchard, A.; Camera, S.; Carbone, C. ...
Astronomy and astrophysics (Berlin),
10/2020, Letnik:
642
Journal Article
Recenzirano
Odprti dostop
Aims.
The
Euclid
space telescope will measure the shapes and redshifts of galaxies to reconstruct the expansion history of the Universe and the growth of cosmic structures. The estimation of the ...expected performance of the experiment, in terms of predicted constraints on cosmological parameters, has so far relied on various individual methodologies and numerical implementations, which were developed for different observational probes and for the combination thereof. In this paper we present validated forecasts, which combine both theoretical and observational ingredients for different cosmological probes. This work is presented to provide the community with reliable numerical codes and methods for
Euclid
cosmological forecasts.
Methods.
We describe in detail the methods adopted for Fisher matrix forecasts, which were applied to galaxy clustering, weak lensing, and the combination thereof. We estimated the required accuracy for
Euclid
forecasts and outline a methodology for their development. We then compare and improve different numerical implementations, reaching uncertainties on the errors of cosmological parameters that are less than the required precision in all cases. Furthermore, we provide details on the validated implementations, some of which are made publicly available, in different programming languages, together with a reference training-set of input and output matrices for a set of specific models. These can be used by the reader to validate their own implementations if required.
Results.
We present new cosmological forecasts for
Euclid
. We find that results depend on the specific cosmological model and remaining freedom in each setting, for example flat or non-flat spatial cosmologies, or different cuts at non-linear scales. The numerical implementations are now reliable for these settings. We present the results for an optimistic and a pessimistic choice for these types of settings. We demonstrate that the impact of cross-correlations is particularly relevant for models beyond a cosmological constant and may allow us to increase the dark energy figure of merit by at least a factor of three.
Euclid preparation Tereno, I.; Dupac, X.; Gómez-Álvarez, P. ...
Astronomy and astrophysics (Berlin),
06/2022, Letnik:
662
Journal Article
Recenzirano
Odprti dostop
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 deg
2
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 deg
2
. The limiting AB magnitudes (5
σ
point-like source) achieved in its footprint are estimated to be 26.2 (visible band
I
E
) and 24.5 (for near infrared bands
Y
E
,
J
E
,
H
E
); for spectroscopy, the H
α
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
.
ABSTRACT
We present a new, updated version of the EuclidEmulator (called EuclidEmulator2), a fast and accurate predictor for the nonlinear correction of the matter power spectrum. 2 per cent level ...accurate emulation is now supported in the eight-dimensional parameter space of w0waCDM+∑mν models between redshift z = 0 and z = 3 for spatial scales within the range $0.01 \, h\, {\rm Mpc}^{-1}\le k \le 10\, h\, {\rm Mpc}^{-1}$. In order to achieve this level of accuracy, we have had to improve the quality of the underlying N-body simulations used as training data: (i) we use self-consistent linear evolution of non-dark matter species such as massive neutrinos, photons, dark energy, and the metric field, (ii) we perform the simulations in the so-called N-body gauge, which allows one to interpret the results in the framework of general relativity, (iii) we run over 250 high-resolution simulations with 30003 particles in boxes of 1(h−1 Gpc)3 volumes based on paired-and-fixed initial conditions, and (iv) we provide a resolution correction that can be applied to emulated results as a post-processing step in order to drastically reduce systematic biases on small scales due to residual resolution effects in the simulations. We find that the inclusion of the dynamical dark energy parameter wa significantly increases the complexity and expense of creating the emulator. The high fidelity of EuclidEmulator2 is tested in various comparisons against N-body simulations as well as alternative fast predictors such as HALOFIT, HMCode, and CosmicEmu. A blind test is successfully performed against the Euclid Flagship v2.0 simulation. Nonlinear correction factors emulated with EuclidEmulator2 are accurate at the level of $1{{\ \rm per\ cent}}$ or better for $0.01 \, h\, {\rm Mpc}^{-1}\le k \le 10\, h\, {\rm Mpc}^{-1}$ and z ≤ 3 compared to high-resolution dark-matter-only simulations. EuclidEmulator2 is publicly available at https://github.com/miknab/EuclidEmulator2.
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.
Euclid
is poised to survey galaxies across a cosmological volume of unprecedented size, providing observations of more than a billion objects distributed over a third of the full sky. Approximately ...20 million of these galaxies will have their spectroscopy available, allowing us to map the three-dimensional large-scale structure of the Universe in great detail. This paper investigates prospects for the detection of cosmic voids therein and the unique benefit they provide for cosmological studies. In particular, we study the imprints of dynamic (redshift-space) and geometric (Alcock–Paczynski) distortions of average void shapes and their constraining power on the growth of structure and cosmological distance ratios. To this end, we made use of the Flagship mock catalog, a state-of-the-art simulation of the data expected to be observed with
Euclid
. We arranged the data into four adjacent redshift bins, each of which contains about 11 000 voids and we estimated the stacked void-galaxy cross-correlation function in every bin. Fitting a linear-theory model to the data, we obtained constraints on
f
/
b
and
D
M
H
, where
f
is the linear growth rate of density fluctuations,
b
the galaxy bias,
D
M
the comoving angular diameter distance, and
H
the Hubble rate. In addition, we marginalized over two nuisance parameters included in our model to account for unknown systematic effects in the analysis. With this approach,
Euclid
will be able to reach a relative precision of about 4% on measurements of
f
/
b
and 0.5% on
D
M
H
in each redshift bin. Better modeling or calibration of the nuisance parameters may further increase this precision to 1% and 0.4%, respectively. Our results show that the exploitation of cosmic voids in
Euclid
will provide competitive constraints on cosmology even as a stand-alone probe. For example, the equation-of-state parameter,
w
, for dark energy will be measured with a precision of about 10%, consistent with previous more approximate forecasts.
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.
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.
Euclid preparation Barnett, R.; Warren, S. J.; Mortlock, D. J. ...
Astronomy and astrophysics (Berlin),
11/2019, Letnik:
631
Journal Article
Recenzirano
Odprti dostop
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 ∝ 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 ∼ 23. Quasars at z > 8 may be selected from Euclid O Y J H 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, 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 ∼ 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 σ uncertainty of 0.07.
ABSTRACT
Next-generation telescopes, like Euclid, Rubin/LSST, and Roman, will open new windows on the Universe, allowing us to infer physical properties for tens of millions of galaxies. ...Machine-learning methods are increasingly becoming the most efficient tools to handle this enormous amount of data, because they are often faster and more accurate than traditional methods. We investigate how well redshifts, stellar masses, and star-formation rates (SFRs) can be measured with deep-learning algorithms for observed galaxies within data mimicking the Euclid and Rubin/LSST surveys. We find that deep-learning neural networks and convolutional neural networks (CNNs), which are dependent on the parameter space of the training sample, perform well in measuring the properties of these galaxies and have a better accuracy than methods based on spectral energy distribution fitting. CNNs allow the processing of multiband magnitudes together with $H_{\scriptscriptstyle \rm E}$-band images. We find that the estimates of stellar masses improve with the use of an image, but those of redshift and SFR do not. Our best results are deriving (i) the redshift within a normalized error of <0.15 for 99.9 ${{\ \rm per\ cent}}$ of the galaxies with signal-to-noise ratio >3 in the $H_{\scriptscriptstyle \rm E}$ band; (ii) the stellar mass within a factor of two ($\sim\!0.3 \rm \ dex$) for 99.5 ${{\ \rm per\ cent}}$ of the considered galaxies; and (iii) the SFR within a factor of two ($\sim\!0.3 \rm \ dex$) for $\sim\!70{{\ \rm per\ cent}}$ of the sample. We discuss the implications of our work for application to surveys as well as how measurements of these galaxy parameters can be improved with deep learning.
PDF
