Euclid preparation van Mierlo, S. E.; Caputi, K. I.; Atek, H. ...
Astronomy and astrophysics (Berlin),
10/2022, Letnik:
666
Journal Article
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Context.
The
Euclid
mission is expected to discover thousands of
z
> 6 galaxies in three deep fields, which together will cover a ∼50 deg
2
area. However, the limited number of
Euclid
bands (four) ...and the low availability of ancillary data could make the identification of
z
> 6 galaxies challenging.
Aims.
In this work we assess the degree of contamination by intermediate-redshift galaxies (
z
= 1–5.8) expected for
z
> 6 galaxies within the Euclid Deep Survey.
Methods.
This study is based on ∼176 000 real galaxies at
z
= 1–8 in a ∼0.7 deg
2
area selected from the UltraVISTA ultra-deep survey and ∼96 000 mock galaxies with 25.3 ≤
H
< 27.0, which altogether cover the range of magnitudes to be probed in the Euclid Deep Survey. We simulate
Euclid
and ancillary photometry from fiducial 28-band photometry and fit spectral energy distributions to various combinations of these simulated data.
Results.
We demonstrate that identifying
z
> 6 galaxies with
Euclid
data alone will be very effective, with a
z
> 6 recovery of 91% (88%) for bright (faint) galaxies. For the UltraVISTA-like bright sample, the percentage of
z
= 1–5.8 contaminants amongst apparent
z
> 6 galaxies as observed with
Euclid
alone is 18%, which is reduced to 4% (13%) by including ultra-deep
Rubin
(
Spitzer
) photometry. Conversely, for the faint mock sample, the contamination fraction with
Euclid
alone is considerably higher at 39%, and minimised to 7% when including ultra-deep
Rubin
data. For UltraVISTA-like bright galaxies, we find that
Euclid
(
I
E
−
Y
E
) > 2.8 and (
Y
E
−
J
E
) < 1.4 colour criteria can separate contaminants from true
z
> 6 galaxies, although these are applicable to only 54% of the contaminants as many have unconstrained (
I
E
−
Y
E
) colours. In the best scenario, these cuts reduce the contamination fraction to 1% whilst preserving 81% of the fiducial
z
> 6 sample. For the faint mock sample, colour cuts are infeasible; we find instead that a 5
σ
detection threshold requirement in at least one of the
Euclid
near-infrared bands reduces the contamination fraction to 25%.
In order to offer an intuitive but effective access to a growing number of cosmological simulations, we have developed the Italian Theoretical Virtual Observatory project (ITVO), as described by ...Pasian and colleagues in 2006. In this work we describe two Web portals as two ways to access and share complex data coming from numerical astrophysical simulations. We present a set of Web services aimed at offering services such as Simple Numeric Access (ProtocolSNAPSimple Numeric Access Protocol), as described by Gheller and colleagues in 2006, and Randomizers dealing with different data formats. The Web services technology allows us to run a particular task (a SNAP job, for instance) close to its data, avoiding an expensive data transfer.
Pair-instability supernovae are theorized supernovae that have not yet been observationally confirmed. They are predicted to exist in low-metallicity environments. Because overall metallicity becomes ...lower at higher redshifts, deep near-infrared transient surveys probing high-redshift supernovae are suitable to discover pair-instability supernovae. The
Euclid
satellite, which is planned launch in 2023, has a near-infrared wide-field instrument that is suitable for a high-redshift supernova survey. The Euclid Deep Survey is planned to make regular observations of three Euclid Deep Fields (40 deg
2
in total) spanning
Euclid
’s six-year primary mission period. While the observations of the Euclid Deep Fields are not frequent, we show that the predicted long duration of pair-instability supernovae would allow us to search for high-redshift pair-instability supernovae with the Euclid Deep Survey. Based on the current observational plan of the
Euclid
mission, we conduct survey simulations in order to estimate the expected numbers of pair-instability supernova discoveries. We find that up to several hundred pair-instability supernovae at
z
≲ 3.5 can be discovered within the Euclid Deep Survey. We also show that pair-instability supernova candidates can be efficiently identified by their duration and color, which can be determined with the current Euclid Deep Survey plan. We conclude that the
Euclid
mission can lead to the first confirmation of pair-instability supernovae if their event rates are as high as those predicted by recent theoretical studies. We also update the expected numbers of superluminous supernova discoveries in the Euclid Deep Survey based on the latest observational plan.
Euclid preparation Bretonnière, H.; Kuchner, U.; Merlin, E. ...
Astronomy and astrophysics (Berlin),
03/2023, Letnik:
671
Journal Article
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The various
Euclid
imaging surveys will become a reference for studies of galaxy morphology by delivering imaging over an unprecedented area of 15 000 square degrees with high spatial resolution. In ...order to understand the capabilities of measuring morphologies from
Euclid
-detected galaxies and to help implement measurements in the pipeline of the Organisational Unit MER of the Euclid Science Ground Segment, we have conducted the Euclid Morphology Challenge, which we present in two papers. While the companion paper focusses on the analysis of photometry, this paper assesses the accuracy of the parametric galaxy morphology measurements in imaging predicted from within the Euclid Wide Survey. We evaluate the performance of five state-of-the-art surface-brightness-fitting codes,
DeepLeGATo
,
Galapagos-2
,
Morfometryka
,
ProFit
and
SourceXtractor++
, on a sample of about 1.5 million simulated galaxies (350 000 above 5
σ
) resembling reduced observations with the
Euclid
VIS and NIR instruments. The simulations include analytic Sérsic profiles with one and two components, as well as more realistic galaxies generated with neural networks. We find that, despite some code-specific differences, all methods tend to achieve reliable structural measurements (< 10% scatter on ideal Sérsic simulations) down to an apparent magnitude of about
I
E
= 23 in one component and
I
E
= 21 in two components, which correspond to a signal-to-noise ratio of approximately 1 and 5, respectively. We also show that when tested on non-analytic profiles, the results are typically degraded by a factor of 3, driven by systematics. We conclude that the official
Euclid
Data Releases will deliver robust structural parameters for at least 400 million galaxies in the Euclid Wide Survey by the end of the mission. We find that a key factor for explaining the different behaviour of the codes at the faint end is the set of adopted priors for the various structural parameters.
Euclid preparation Castellano, M.; Huertas-Company, M.; Kuchner, U. ...
Astronomy and astrophysics (Berlin),
03/2023, Letnik:
671
Journal Article
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The European Space Agency's
Euclid
mission will provide high-quality imaging for about 1.5 billion galaxies. A software pipeline to automatically process and analyse such a huge amount of data in ...real time is being developed by the Science Ground Segment of the Euclid Consortium; this pipeline will include a model-fitting algorithm, which will provide photometric and morphological estimates of paramount importance for the core science goals of the mission and for legacy science. The
Euclid
Morphology Challenge is a comparative investigation of the performance of five model-fitting software packages on simulated
Euclid
data, aimed at providing the baseline to identify the best-suited algorithm to be implemented in the pipeline. In this paper we describe the simulated dataset, and we discuss the photometry results. A companion paper is focussed on the structural and morphological estimates. We created mock
Euclid
images simulating five fields of view of 0.48 deg
2
each in the
I
E
band of the VIS instrument, containing a total of about one and a half million galaxies (of which 350 000 have a nominal signal-to-noise ratio above 5), each with three realisations of galaxy profiles (single and double Sérsic, and 'realistic' profiles obtained with a neural network); for one of the fields in the double Sérsic realisation, we also simulated images for the three near-infrared
Y
E
,
J
E
, and
H
E
bands of the NISP-P instrument, and five Rubin/LSST optical complementary bands (
u
,
g, r, i,
and
z
), which together form a typical dataset for an
Euclid
observation. The images were simulated at the expected
Euclid
Wide Survey depths. To analyse the results, we created diagnostic plots and defined metrics to take into account the completeness of the provided catalogues, as well as the median biases, dispersions, and outlier fractions of their measured flux distributions. Five model-fitting software packages (
DeepLeGATo
,
Galapagos-2
,
Morfometryka
,
ProFit
, and
SourceXtractor++
) were compared, all typically providing good results. Of the differences among them, some were at least partly due to the distinct strategies adopted to perform the measurements. In the best-case scenario, the median bias of the measured fluxes in the analytical profile realisations is below 1% at a signal-to-noise ratio above 5 in
I
E
, and above 10 in all the other bands; the dispersion of the distribution is typically comparable to the theoretically expected one, with a small fraction of catastrophic outliers. However, we can expect that real observations will prove to be more demanding, since the results were found to be less accurate for the most realistic realisation. We conclude that existing model-fitting software can provide accurate photometric measurements on
Euclid
datasets. The results of the challenge are fully available and reproducible through an online plotting tool.
Euclid preparation Huertas-Company, M.; Lanusse, F.; Jullo, E. ...
Astronomy and astrophysics (Berlin),
01/2022, Letnik:
657
Journal Article
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We present a machine learning framework to simulate realistic galaxies for the
Euclid
Survey, producing more complex and realistic galaxies than the analytical simulations currently used in
Euclid
. ...The proposed method combines a control on galaxy shape parameters offered by analytic models with realistic surface brightness distributions learned from real
Hubble
Space Telescope observations by deep generative models. We simulate a galaxy field of 0.4 deg
2
as it will be seen by the
Euclid
visible imager VIS, and we show that galaxy structural parameters are recovered to an accuracy similar to that for pure analytic Sérsic profiles. Based on these simulations, we estimate that the
Euclid
Wide Survey (EWS) will be able to resolve the internal morphological structure of galaxies down to a surface brightness of 22.5 mag arcsec
−2
, and the
Euclid
Deep Survey (EDS) down to 24.9 mag arcsec
−2
. This corresponds to approximately 250 million galaxies at the end of the mission and a 50% complete sample for stellar masses above 10
10.6
M
⊙
(resp. 10
9.6
M
⊙
) at a redshift
z
∼ 0.5 for the EWS (resp. EDS). The approach presented in this work can contribute to improving the preparation of future high-precision cosmological imaging surveys by allowing simulations to incorporate more realistic galaxies.
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. The standard cosmological model is based on the fundamental assumptions of a spatially homogeneous and isotropic universe on large scales. An observational detection of a violation of these ...assumptions at any redshift would immediately indicate the presence of new physics.
Aims. We quantify the ability of the Euclid mission, together with contemporary surveys, to improve the current sensitivity of null tests of the canonical cosmological constant Λ and the cold dark matter (ΛCDM) model in the redshift range 0 < z < 1.8.
Methods. We considered both currently available data and simulated Euclid and external data products based on a ΛCDM fiducial model, an evolving dark energy model assuming the Chevallier-Polarski-Linder parameterization or an inhomogeneous Lemaître-Tolman-Bondi model with a cosmological constant Λ, and carried out two separate but complementary analyses: a machine learning reconstruction of the null tests based on genetic algorithms, and a theory-agnostic parametric approach based on Taylor expansion and binning of the data, in order to avoid assumptions about any particular model.
Results. We find that in combination with external probes, Euclid can improve current constraints on null tests of the ΛCDM by approximately a factor of three when using the machine learning approach and by a further factor of two in the case of the parametric approach. However, we also find that in certain cases, the parametric approach may be biased against or missing some features of models far from ΛCDM.
Conclusions. Our analysis highlights the importance of synergies between Euclid and other surveys. These synergies are crucial for providing tighter constraints over an extended redshift range for a plethora of different consistency tests of some of the main assumptions of the current cosmological paradigm.
Euclid preparation Humphrey, A.; Bolzonella, M.; Fotopoulou, S. ...
Astronomy and astrophysics (Berlin),
03/2023, Letnik:
671
Journal Article
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The
Euclid
Space Telescope will provide deep imaging at optical and near-infrared wavelengths, along with slitless near-infrared spectroscopy, across ~15 000deg
2
of the sky.
Euclid
is expected to ...detect ~12 billion astronomical sources, facilitating new insights into cosmology, galaxy evolution, and various other topics. In order to optimally exploit the expected very large dataset, appropriate methods and software tools need to be developed. Here we present a novel machine-learning-based methodology for the selection of quiescent galaxies using broadband
Euclid I
E
,
Y
E
,
J
E
, and
H
E
photometry, in combination with multi-wavelength photometry from other large surveys (e.g. the
Rubin
LSST). The ARIADNE pipeline uses meta-learning to fuse decision-tree ensembles, nearest-neighbours, and deep-learning methods into a single classifier that yields significantly higher accuracy than any of the individual learning methods separately. The pipeline has been designed to have 'sparsity awareness', such that missing photometry values are informative for the classification. In addition, our pipeline is able to derive photometric redshifts for galaxies selected as quiescent, aided by the 'pseudo-labelling' semi-supervised method, and using an outlier detection algorithm to identify and reject likely catastrophic outliers. After the application of the outlier filter, our pipeline achieves a normalised mean absolute deviation of ≲0.03 and a fraction of catastrophic outliers of ≲0.02 when measured against the COSMOS2015 photometric redshifts. We apply our classification pipeline to mock galaxy photometry catalogues corresponding to three main scenarios: (i)
Euclid
Deep Survey photometry with ancillary
ugriz,
WISE, and radio data; (ii)
Euclid
Wide Survey photometry with ancillary
ugriz,
WISE, and radio data; and (iii)
Euclid
Wide Survey photometry only, with no foreknowledge of galaxy redshifts. In a like-for-like comparison, our classification pipeline outperforms
UVJ
selection, in addition to the
Euclid I
E
–
Y
E
,
J
E
–
H
E
and
u
–
I
E
, I
E
–
J
E
colour-colour methods, with improvements in completeness and the
F
1-score (the harmonic mean of precision and recall) of up to a factor of 2.
Primordial features, in particular oscillatory signals, imprinted in the primordial power spectrum of density perturbations represent a clear window of opportunity for detecting new physics at ...high-energy scales. Future spectroscopic and photometric measurements from the
Euclid
space mission will provide unique constraints on the primordial power spectrum, thanks to the redshift coverage and high-accuracy measurement of nonlinear scales, thus allowing us to investigate deviations from the standard power-law primordial power spectrum. We consider two models with primordial undamped oscillations superimposed on the matter power spectrum described by 1 +
X
sin (
ω
X
Ξ
X
+ 2
πϕ
X
), one linearly spaced in
k
space with Ξ
lin
≡
k
/
k
*
where
k
*
= 0.05 Mpc
−1
and the other logarithmically spaced in
k
space with Ξ
log
≡ ln(
k
/
k
*
). We note that
X
is the amplitude of the primordial feature,
ω
X
is the dimensionless frequency, and
ϕ
X
is the normalised phase, where
X
= {lin, log}. We provide forecasts from spectroscopic and photometric primary
Euclid
probes on the standard cosmological parameters Ω
m, 0
, Ω
b, 0
,
h
,
n
s
, and
σ
8
, and the primordial feature parameters
X
,
ω
X
, and
ϕ
X
. We focus on the uncertainties of the primordial feature amplitude
X
and on the capability of
Euclid
to detect primordial features at a given frequency. We also study a nonlinear density reconstruction method in order to retrieve the oscillatory signals in the primordial power spectrum, which are damped on small scales in the late-time Universe due to cosmic structure formation. Finally, we also include the expected measurements from
Euclid
’s galaxy-clustering bispectrum and from observations of the cosmic microwave background (CMB). We forecast uncertainties in estimated values of the cosmological parameters with a Fisher matrix method applied to spectroscopic galaxy clustering (GC
sp
), weak lensing (WL), photometric galaxy clustering (GC
ph
), the cross correlation (XC) between GC
ph
and WL, the spectroscopic galaxy clustering bispectrum, the CMB temperature and
E
-mode polarisation, the temperature-polarisation cross correlation, and CMB weak lensing. We consider two sets of specifications for the
Euclid
probes (pessimistic and optimistic) and three different CMB experiment configurations, that is,
Planck
, Simons Observatory (SO), and CMB Stage-4 (CMB-S4). We find the following percentage relative errors in the feature amplitude with
Euclid
primary probes: for the linear (logarithmic) feature model, with a fiducial value of
X
= 0.01,
ω
X
= 10, and
ϕ
X
= 0: 21% (22%) in the pessimistic settings and 18% (18%) in the optimistic settings at a 68.3% confidence level (CL) using GC
sp
+WL+GC
ph
+XC. While the uncertainties on the feature amplitude are strongly dependent on the frequency value when single
Euclid
probes are considered, we find robust constraints on
X
from the combination of spectroscopic and photometric measurements over the frequency range of (1, 10
2.1
). Due to the inclusion of numerical reconstruction, the GC
sp
bispectrum, SO-like CMB reduces the uncertainty on the primordial feature amplitude by 32%–48%, 50%–65%, and 15%–50%, respectively. Combining all the sources of information explored expected from
Euclid
in combination with the future SO-like CMB experiment, we forecast
lin
≃ 0.010 ± 0.001 at a 68.3% CL and
log
≃ 0.010 ± 0.001 for GC
sp
(PS rec + BS)+WL+GC
ph
+XC+SO-like for both the optimistic and pessimistic settings over the frequency range (1, 10
2.1
).
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