Abstract
A simple method for calculating a low-resolution power spectrum from data with gaps is described. The method is a modification of the Δ-variance method previously described by Stutzki and ...Ossenkopf. A Mexican hat filter is used to single out fluctuations at a given spatial scale, and the variance of the convolved image is calculated. The gaps in the image, defined by the mask, are corrected for by representing the Mexican hat filter as a difference between two Gaussian filters with slightly different widths, convolving the image and mask with these filters and dividing the results before calculating the final filtered image. This method cleanly compensates for data gaps even if these have complicated shapes and cover a significant fraction of the data. The method was developed to deal with problematic 2D images, where irregular detector edges and masking of contaminating sources compromise the power spectrum estimates, but it can also be straightforwardly applied to 1D timing analysis or 3D data cubes from numerical simulations.
This Voyage 2050 paper highlights the unique science opportunities using spectral distortions of the cosmic microwave background (CMB). CMB spectral distortions probe many processes throughout the ...history of the Universe, delivering novel information that complements past, present and future efforts with CMB anisotropy and large-scale structure studies. Precision spectroscopy, possible with existing technology, would not only provide key tests for processes expected within the cosmological standard model but also open an enormous discovery space to new physics. This offers unique scientific opportunities for furthering our understanding of inflation, recombination, reionization and structure formation as well as dark matter and particle physics. A dedicated experimental approach could open this new window to the early Universe in the decades to come, allowing us to turn the long-standing upper distortion limits obtained with
COBE
/FIRAS some 25 years ago into clear detections of the expected standard distortion signals and also challenge our current understanding of the laws of nature.
Aims. We present the photometric calibration of the 12 optical passbands observed by the Javalambre Photometric Local Universe Survey (J-PLUS). Methods. The proposed calibration method has four ...steps: (i) definition of a high-quality set of calibration stars using Gaia information and available 3D dust maps; (ii) anchoring of the J-PLUS gri passbands to the Pan-STARRS photometric solution, accounting for the variation in the calibration with the position of the sources on the CCD; (iii) homogenization of the photometry in the other nine J-PLUS filters using the dust de-reddened instrumental stellar locus in (𝒳 − r) versus (g − i) colours, where 𝒳 is the filter to calibrate. The zero point variation along the CCD in these filters was estimated with the distance to the stellar locus. Finally, (iv) the absolute colour calibration was obtained with the white dwarf locus. We performed a joint Bayesian modelling of 11 J-PLUS colour–colour diagrams using the theoretical white dwarf locus as reference. This provides the needed offsets to transform instrumental magnitudes to calibrated magnitudes outside the atmosphere. Results. The uncertainty of the J-PLUS photometric calibration, estimated from duplicated objects observed in adjacent pointings and accounting for the absolute colour and flux calibration errors, are ∼19 mmag in u, J0378, and J0395; ∼11 mmag in J0410 and J0430; and ∼8 mmag in g, J0515, r, J0660, i, J0861, and z. Conclusions. We present an optimized calibration method for the large-area multi-filter J-PLUS project, reaching 1–2% accuracy within an area of 1022 square degrees without the need for long observing calibration campaigns or constant atmospheric monitoring. The proposed method will be adapted for the photometric calibration of J-PAS, that will observe several thousand square degrees with 56 narrow optical filters.
Since the publication of the results of the Planck satellite mission in 2013, the local and early Universes have been considered to be in tension in respect of the determination of amplitude of the ...matter density spatial fluctuations (σ8) and the amount of matter present in the Universe (Ωm). This tension can be seen as a lack of massive galaxy clusters in the local Universe compared to the prediction inferred from Planck cosmic microwave background (CMB) best-fitting cosmology. In the present analysis we perform the first detection of the cross-correlation between X-rays and CMB weak lensing at 9.1σ. We next combine thermal Sunyaev–Zel’dovich effect, X-rays, and weak-lensing angular auto- and cross-correlation power spectra to determine the galaxy cluster hydrostatic mass bias. We derive (1 − bH) = 0.71 ± 0.07. Considering these constraints, we observe that estimations of σ8 in the local Universe are consistent with Planck CMB best-fitting cosmology. However, these results are in clear tension with the output of hydrodynamical simulations that favor (1 − bH)> 0.8.
If dark energy introduces an acceleration in the universal expansion then large-scale gravitational potential wells should be shrinking, causing a blueshift in the cosmic microwave background (CMB) ...photons that cross such structures integrated Sachs-Wolfe (ISW) effect. Galaxy clusters are known to probe those potential wells. In these objects, CMB photons also experience inverse Compton scattering off the hot electrons of the intracluster medium and this results in a distortion with a characteristic spectral signature of the CMB spectrum the so-called thermal Sunyaev-Zel'dovich (tSZ) effect. Since both the ISW and the tSZ effects take place in the same potential wells, they must be spatially correlated. We present how this cross-ISW-tSZ signal can be detected in a CMB data contained way by using the frequency dependence of the tSZ effect in multifrequency CMB experiments like Planck, without requiring the use of external large-scale structure tracers data. We find that by masking low-redshift clusters, the shot noise level decreases significantly, boosting the signal-to-noise ratio of the ISW-tSZ cross-correlation. Nevertheless, in a more realistic case in which we only mask the clusters that could be detected by Planck, detection of the ISW-tSZ cross-signal is expected to reach only low significance (1.5σ) unless external cluster catalogues are used to mask the tSZ signal coming from lower mass clusters at low z that do not significantly contribute to the signal but to the shot noise. We also find that galactic and extragalactic dust residuals must be kept at or below the level of ∼0.04 (μK)2 at ℓ= 10, a limit that is a factor of a few below Planck's expectations for foreground subtraction. If this is achieved, CMB observations of the ISW-tSZ cross-correlation should also provide an independent probe for the existence of dark energy and the amplitude of density perturbations.
In the context of the study of the integrated Sachs Wolfe effect (ISW), we revisit the angular cross correlation of WMAP cosmic microwave background (CMB) data with the NRAO Very Large Array Sky ...Survey (NVSS). We compute 2-point cross functions between the two surveys, both in real and in Fourier space, paying particular attention on the dependence of results on the flux of NVSS radio sources, the angular scales where correlations arise and the comparison with theoretical expectations. We reproduce previous results that claim an excess of correlation in the angular correlation function (ACF), and we also find some (low significance, ~2-σ) similarity between the CMB and radio galaxy data in the multipole range l ∈ 10, 25. However, the signal to noise ratio (S/N) in the ACFs increases with higher flux thresholds for NVSS sources, but drops a ~ 30–50% in separations of the order of a pixel size, suggesting some residual point source contribution. When restricting our analyses to multipoles l < 60, we fail to find any evidence for cross correlation in the range l ∈ 2,10, where according to the model predictions and our simulations ~ 50% of the S/N is supposed to arise. Also, the accumulated S/N for l<60 is below 1, far from the theoretical expectation of S/N ~ 5. Part of this disagreement may be caused by an inaccurate modeling of the NVSS source population: as in previous works, we find a level of large scale (l < 70) clustering in the NVSS catalog that seems incompatible with a high redshift population. This large scale clustering excess is unlikely to be caused by contaminants or systematics, since it is independent of flux threshold, and hence present for the brightest, most clearly detected (> 30σ) NVSS sources. Either our NVSS catalogs are not probing the high redshift, large scale gravitational potential wells, or there is a clear mismatch between the ISW component present in WMAP data and theoretical expectations.
Aims.
We estimated the spectral evolution of white dwarfs with effective temperature using the Javalambre Photometric Local Universe Survey (J-PLUS) second data release (DR2), which provides 12 ...photometric optical passbands over 2176 deg
2
.
Methods.
We analyzed 5926 white dwarfs with
r
≤ 19.5 mag in common between a white dwarf catalog defined from
Gaia
EDR3 and J-PLUS DR2. We performed a Bayesian analysis by comparing the observed J-PLUS photometry with theoretical models of hydrogen- and helium-dominated atmospheres. We estimated the probability distribution functions for effective temperature (
T
eff
), surface gravity, parallax, and composition; and the probability of having a H-dominated atmosphere (
p
H
) for each source. We applied a prior in parallax, using
Gaia
EDR3 measurements as a reference, and derived a self-consistent prior for the atmospheric composition as a function of
T
eff
.
Results.
We described the fraction of white dwarfs with a He-dominated atmosphere (
f
He
) with a linear function of the effective temperature at 5000 <
T
eff
< 30 000 K. We find
f
He
= 0.24 ± 0.01 at
T
eff
= 10 000 K, a change rate along the cooling sequence of 0.14 ± 0.02 per 10 kK, and a minimum He-dominated fraction of 0.08 ± 0.02 at the high-temperature end. We tested the obtained
p
H
by comparison with spectroscopic classifications, finding that it is reliable. We estimated the mass distribution for the 351 sources with distance
d
< 100 pc, mass
M
> 0.45
M
⊙
, and
T
eff
> 6000 K. The result for H-dominated white dwarfs agrees with previous studies, with a dominant
M
= 0.59
M
⊙
peak and the presence of an excess at
M
∼ 0.8
M
⊙
. This high-mass excess is absent in the He-dominated distribution, which presents a single peak.
Conclusions.
The J-PLUS optical data provide a reliable statistical classification of white dwarfs into H- and He-dominated atmospheres. We find a 21 ± 3% increase in the fraction of He-dominated white dwarfs from
T
eff
= 20 000 K to
T
eff
= 5000 K.
Context. Future astrophysical surveys such as J-PAS will produce very large datasets, the so-called “big data”, which will require the deployment of accurate and efficient machine-learning (ML) ...methods. In this work, we analyze the miniJPAS survey, which observed about ∼1 deg 2 of the AEGIS field with 56 narrow-band filters and 4 u g r i broad-band filters. The miniJPAS primary catalog contains approximately 64 000 objects in the r detection band (mag A B ≲ 24), with forced-photometry in all other filters. Aims. We discuss the classification of miniJPAS sources into extended (galaxies) and point-like (e.g., stars) objects, which is a step required for the subsequent scientific analyses. We aim at developing an ML classifier that is complementary to traditional tools that are based on explicit modeling. In particular, our goal is to release a value-added catalog with our best classification. Methods. In order to train and test our classifiers, we cross-matched the miniJPAS dataset with SDSS and HSC-SSP data, whose classification is trustworthy within the intervals 15 ≤ r ≤ 20 and 18.5 ≤ r ≤ 23.5, respectively. We trained and tested six different ML algorithms on the two cross-matched catalogs: K-nearest neighbors, decision trees, random forest (RF), artificial neural networks, extremely randomized trees (ERT), and an ensemble classifier. This last is a hybrid algorithm that combines artificial neural networks and RF with the J-PAS stellar and galactic loci classifier. As input for the ML algorithms we used the magnitudes from the 60 filters together with their errors, with and without the morphological parameters. We also used the mean point spread function in the r detection band for each pointing. Results. We find that the RF and ERT algorithms perform best in all scenarios. When the full magnitude range of 15 ≤ r ≤ 23.5 is analyzed, we find an area under the curve AUC = 0.957 with RF when photometric information alone is used, and AUC = 0.986 with ERT when photometric and morphological information is used together. When morphological parameters are used, the full width at half maximum is the most important feature. When photometric information is used alone, we observe that broad bands are not necessarily more important than narrow bands, and errors (the width of the distribution) are as important as the measurements (central value of the distribution). In other words, it is apparently important to fully characterize the measurement. Conclusions. ML algorithms can compete with traditional star and galaxy classifiers; they outperform the latter at fainter magnitudes ( r ≳ 21). We use our best classifiers, with and without morphology, in order to produce a value-added catalog.
In the context of next-generation spectroscopic galaxy surveys, new statistics of the distribution of matter are currently being developed. Among these, we investigated the angular redshift ...fluctuations (ARF), which probe the information contained in the projected redshift distribution of galaxies. Relying on the Fisher formalism, we show how ARF will provide complementary cosmological information compared to traditional angular galaxy clustering. We tested both the standard ΛCDM model and the wCDM extension. We find that the cosmological and galaxy bias parameters express different degeneracies when inferred from ARF or from angular galaxy clustering. As such, combining both observables breaks these degeneracies and greatly decreases the marginalised uncertainties by a factor of at least two on most parameters for the ΛCDM and wCDM models. We find that the ARF combined with angular galaxy clustering provide a great way to probe dark energy by increasing the figure of merit of the
w
0
−
w
a
parameter set by a factor of more than ten compared to angular galaxy clustering alone. Finally, we compared ARF to the CMB lensing constraints on the galaxy bias parameters. We show that a joint analysis of ARF and angular galaxy clustering improves constraints by ∼40% on galaxy bias compared to a joint analysis of angular galaxy clustering and CMB lensing.
MiniJPAS is a ∼1 deg
2
imaging survey of the AEGIS field in 60 bands, performed to demonstrate the scientific potential of the upcoming Javalambre-Physics of the Accelerating Universe Astrophysical ...Survey (J-PAS). Full coverage of the 3800–9100 Å range with 54 narrow-band filters, in combination with 6 optical broad-band filters, allows for extremely accurate photometric redshifts (photo-
z
), which, applied over areas of thousands of square degrees, will enable new applications of the photo-
z
technique, such as measurement of baryonic acoustic oscillations. In this paper we describe the method we used to obtain the photo-
z
that is included in the publicly available miniJPAS catalogue, and characterise the photo-
z
performance. We built photo-spectra with 100 Å resolution based on forced-aperture photometry corrected for point spread function. Systematic offsets in the photometry were corrected by applying magnitude shifts obtained through iterative fitting with stellar population synthesis models. We computed photo-
z
with a customised version of L
E
P
HARE
, using a set of templates that is optimised for the J-PAS filter-set. We analysed the accuracy of miniJPAS photo-
z
and their dependence on multiple quantities using a subsample of 5266 galaxies with spectroscopic redshifts from SDSS and DEEP, which we find to be representative of the whole
r
< 23 miniJPAS sample. Formal 1
σ
uncertainties for the photo-
z
that are calculated with the Δ
χ
2
method underestimate the actual redshift errors. The
o
d
d
s
parameter has a stronger correlation with |Δ
z
| and accurately reproduces the probability of a redshift outlier (|Δ
z
| > 0.03), regardless of the magnitude, redshift, or spectral type of the sources. We show that the two main summary statistics characterising the photo-
z
accuracy for a population of galaxies (
σ
NMAD
and
η
) can be predicted by the distribution of
o
d
d
s
in this population, and we use this to estimate the statistics for the whole miniJPAS sample. At
r
< 23, there are ∼17 500 galaxies per deg
2
with valid photo-
z
estimates, ∼4200 of which are expected to have |Δ
z
| < 0.003. The typical error is
σ
NMAD
= 0.013 with an outlier rate
η
= 0.39. The target photo-
z
accuracy
σ
NMAD
= 0.003 is achieved for
o
d
d
s
> 0.82 with
η
= 0.05, at the cost of decreasing the density of selected galaxies to
n
∼ 5200 deg
−2
(∼2600 of which have |Δ
z
| < 0.003).
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