scholarly journals HIR4: cosmological signatures imprinted on the cross-correlation between a 21-cm map and galaxy clustering

2020 ◽  
Vol 499 (4) ◽  
pp. 4613-4625
Author(s):  
Feng Shi ◽  
Yong-Seon Song ◽  
Jacobo Asorey ◽  
David Parkinson ◽  
Kyungjin Ahn ◽  
...  
Keyword(s):  
Power Spectrum ◽  
Cross Correlation ◽  
Broad Band ◽  
Power Spectra ◽  
Acoustic Oscillation ◽  
Particle Simulation ◽  
Band Shape ◽  
Angular Diameter Distance ◽  
Instrument Noise ◽  
The Cross

ABSTRACT We explore the cosmological multitracer synergies between an emission-line galaxy distribution from the Dark Energy Spectroscopic Instrument and a Tianlai Project 21-cm intensity map. We use simulated maps generated from a particle simulation in the light-cone volume (Horizon Run 4), sky-trimmed and including the effects of foreground contamination, its removal and instrument noise. We first validate how the foreground residual affects the recovered 21-cm signal by putting different levels of foreground contamination into the 21-cm maps. We find that the contamination cannot be ignored in the angular autocorrelation power spectra of H i even when it is small, but it has no influence on the accuracy of the angular cross-correlation power spectra between H i and galaxies. In the foreground-cleaned map case, as information is lost in the cleaning procedure, there is also a bias in the cross-correlation power spectrum. However, we found that the bias from the cross-correlation power spectrum is scale-independent, which is easily parametrized as part of the model, while the offset in the H i autocorrelation power spectrum is non-linear. In particular, we tested that the cross-correlation power also benefits from the cancellation of the bias in the power spectrum measurement that is induced by the instrument noise, which changes the shape of the autocorrelation power spectra but leaves the cross-correlation power spectra unaffected. We then modelled the angular cross-correlation power spectra to fit the baryon acoustic oscillation feature in the broad-band shape of the angular cross-correlation power spectrum, including contamination from the residual foreground and the effect of instrument noise. We forecast a constraint on the angular diameter distance DA for the Tianlai Pathfinder redshift 0.775 < z < 1.03, giving a distance measurement with a precision of 2.7 per cent at that redshift.

scholarly journals The clustering of the SDSS-IV extended baryon oscillation spectroscopic survey DR16 luminous red galaxy and emission-line galaxy samples: cosmic distance and structure growth measurements using multiple tracers in configuration space

2020 ◽  
Vol 498 (3) ◽  
pp. 3470-3483 ◽  
Author(s):  
Yuting Wang ◽  
Gong-Bo Zhao ◽  
Cheng Zhao ◽  
Oliver H E Philcox ◽  
Shadab Alam ◽  
...  
Keyword(s):  
Emission Line ◽  
Configuration Space ◽  
Cross Correlation ◽  
Acoustic Oscillation ◽  
Sloan Digital Sky Survey ◽  
Joint Measurement ◽  
Angular Diameter Distance ◽  
Two Samples ◽  
Space Distortion ◽  
Line Galaxy

ABSTRACT We perform a multitracer analysis using the complete Sloan Digital Sky Survey IV (SDSS-IV) extended Baryon Oscillation Spectroscopic Survey (eBOSS) DR16 luminous red galaxy (LRG) and the DR16 emission-line galaxy (ELG) samples in the configuration space, and successfully detect a cross-correlation between the two samples, and find the growth rate to be fσ8=0.342 ± 0.085 (∼25 per cent accuracy) from the cross-sample alone. We perform a joint measurement of the baryonic acoustic oscillation (BAO) and redshift space distortion (RSD) parameters at a single effective redshift of zeff = 0.77, using the autocorrelation and cross-correlation functions of the LRG and ELG samples, and find that the comoving angular diameter distance DM(zeff)/rd = 18.85 ± 0.38, the Hubble distance DH(zeff)/rd = 19.64 ± 0.57, and fσ8(zeff) = 0.432 ± 0.038, which is consistent with a ΛCDM model at $68{\ \rm per\ cent}$ CL. Compared to the single-tracer analysis on the LRG sample, the Figure of Merit of α⊥, α∥, andfσ8 is improved by a factor of 1.11 in our multitracer analysis, and in particular, the statistical uncertainty of fσ8 is reduced by $11.6{\ \rm per\ cent}$.

scholarly journals Multi-waveband detection of quasi-periodic pulsations in a stellar flare on EK Draconis observed by XMM-Newton

2019 ◽  
Vol 629 ◽  
pp. A147 ◽  
Author(s):  
A.-M. Broomhall ◽  
A. E. L. Thomas ◽  
C. E. Pugh ◽  
J. P. Pye ◽  
S. R. Rosen
Keyword(s):  
Energy Band ◽  
Cross Correlation ◽  
Power Spectra ◽  
High Energy ◽  
Low Energy ◽  
The Sun ◽  
Energy Bands ◽  
X Ray ◽  
High Energy Band ◽  
The Cross

Context. Quasi-periodic pulsations (QPPs) are time variations in the energy emission during a flare that are observed on both the Sun and other stars and thus have the potential to link the physics of solar and stellar flares. Aims. We characterise the QPPs detected in an X-ray flare on the solar analogue, EK Draconis, which was observed by XMM-Newton. Methods. We used wavelet and autocorrelation techniques to identify the QPPs in a detrended version of the flare. We also fitted a model to the flare based on an exponential decay combined with a decaying sinusoid. The flare is examined in multiple energy bands. Results. A statistically significant QPP is observed in the X-ray energy band of 0.2–12.0 keV with a periodicity of 76 ± 2 min. When this energy band is split, a statistically significant QPP is observed in the low-energy band (0.2–1.0 keV) with a periodicity of 73 ± 2 min and in the high-energy band (1.0–12.0 keV) with a periodicity of 82 ± 2 min. When fitting a model to the time series the phases of the signals are also found to be significantly different in the two energy bands (with a difference of 1.8 ± 0.2 rad) and the high-energy band is found to lead the low-energy band. Furthermore, the first peak in the cross-correlation between the detrended residuals of the low- and high-energy bands is offset from zero by more than 3σ (4.1 ± 1.3 min). Both energy bands produce statistically significant regions in the wavelet spectrum, whose periods are consistent with those listed above. However, the peaks are broad in both the wavelet and global power spectra, with the wavelet showing evidence for a drift in period with time, and the difference in period obtained is not significant. The offset in the first peak in the cross-correlation of the detrended residuals of two non-congruent energy bands (0.5−1.0 keV and 4.5−12.0 keV) is found to be even larger (10 ± 2 min). However, the signal-to-noise in the higher of these two energy-bands, covering the range 4.5−12.0 keV, is low. Conclusions. The presence of QPPs similar to those observed on the Sun, and other stars, suggests that the physics of flares on this young solar analogue is similar to the physics of solar flares. It is possible that the differences in the QPPs detected in the two energy bands are seen because each band observes a different plasma structure. However, the phase difference, which differs more significantly between the two energy bands than the period, could also be explained in terms of the Neupert effect. This suggests that QPPs are caused by the modulation of the propagation speeds of charged particles.

scholarly journals Simple halo model formalism for the cosmic infrared background and its correlation with the thermal Sunyaev-Zel’dovich effect

2021 ◽  
Vol 645 ◽  
pp. A40
Author(s):  
A. Maniyar ◽  
M. Béthermin ◽  
G. Lagache
Keyword(s):  
Star Formation ◽  
Power Spectrum ◽  
Cross Correlation ◽  
Power Spectra ◽  
Star Formation History ◽  
Maximum Efficiency ◽  
Infrared Background ◽  
Cosmic Infrared Background ◽  
The One ◽  
Model Formalism

Modelling the anisotropies in the cosmic infrared background (CIB) on all the scales is a challenging task because the nature of the galaxy evolution is complex and too many parameters are therefore often required to fit the observational data. We present a new halo model for the anisotropies of the CIB using only four parameters. Our model connects the mass accretion on the dark matter haloes to the star formation rate. Despite its relative simplicity, it is able to fit both the Planck and Herschel CIB power spectra and is consistent with the external constraints for the obscured star formation history derived from infrared deep surveys used as priors for the fit. Using this model, we find that the halo mass with the maximum efficiency for converting the accreted baryons into stars is log10Mmax = 12.94-0.02+0.02 M⊙, consistent with other studies. Accounting for the mass loss through stellar evolution, we find for an intermediate-age galaxy that the star formation efficiency defined as M⋆(z)/Mb(z) is equal to 0.19 and 0.21 at redshift 0.1 and 2, respectively, which agrees well with the values obtained by previous studies. A CIB model is used for the first time to simultaneously fit Planck and Herschel CIB power spectra. The high angular resolution of Herschel allows us to reach very small scales, making it possible to constrain the shot noise and the one-halo term separately, which is difficult to do using the Planck data alone. However, we find that large angular scale Planck and Herschel data are not fully compatible with the small-scale Herschel data (for ℓ >  3000). The CIB is expected to be correlated with the thermal Sunyaev-Zel’dovich (tSZ) signal of galaxy clusters. Using this halo model for the CIB and a halo model for the tSZ with a single parameter, we also provide a consistent framework for calculating the CIB × tSZ cross correlation, which requires no additional parameter. To a certain extent, the CIB at high frequencies traces galaxies at low redshifts that reside in the clusters contributing to the tSZ, giving rise to the one-halo term of this correlation, while the two-halo term comes from the overlap in the redshift distribution of the tSZ clusters and CIB galaxies. The CIB × tSZ correlation is thus found to be higher when inferred with a combination of two widely spaced frequency channels (e.g. 143 × 857 GHz). We also find that even at ℓ ∼ 2000, the two-halo term of this correlation is still comparable to the one-halo term and has to be accounted for in the total cross-correlation. The CIB, tSZ, and CIB × tSZ act as foregrounds when the kinematic SZ (kSZ) power spectrum is measured from the cosmic microwave background power spectrum and need to be removed. Because of its simplistic nature and the low number of parameters, the halo model formalism presented here for these foregrounds is quite useful for such an analysis to measure the kSZ power spectrum accurately.

scholarly journals Planck 2018 results

2020 ◽  
Vol 641 ◽  
pp. A8 ◽  
Author(s):  
◽  
N. Aghanim ◽  
Y. Akrami ◽  
M. Ashdown ◽  
J. Aumont ◽  
...  
Keyword(s):  
Power Spectrum ◽  
High Redshift ◽  
Cosmological Parameters ◽  
Power Spectra ◽  
Acoustic Oscillation ◽  
Minimum Variance ◽  
Baryon Density ◽  
Small Scale ◽  
Individual Parameter ◽  
Parameter Constraints

We present measurements of the cosmic microwave background (CMB) lensing potential using the final Planck 2018 temperature and polarization data. Using polarization maps filtered to account for the noise anisotropy, we increase the significance of the detection of lensing in the polarization maps from 5σ to 9σ. Combined with temperature, lensing is detected at 40σ. We present an extensive set of tests of the robustness of the lensing-potential power spectrum, and construct a minimum-variance estimator likelihood over lensing multipoles 8 ≤ L ≤ 400 (extending the range to lower L compared to 2015), which we use to constrain cosmological parameters. We find good consistency between lensing constraints and the results from the Planck CMB power spectra within the ΛCDM model. Combined with baryon density and other weak priors, the lensing analysis alone constrains σ8Ωm0.25 = 0.589 ± 0.020 (1σ errors). Also combining with baryon acoustic oscillation data, we find tight individual parameter constraints, σ8 = 0.811 ± 0.019, H0 = 67.9−1.3+1.2 km s−1 Mpc−1, and Ωm = 0.303−0.018+0.016. Combining with Planck CMB power spectrum data, we measure σ8 to better than 1% precision, finding σ8 = 0.811 ± 0.006. CMB lensing reconstruction data are complementary to galaxy lensing data at lower redshift, having a different degeneracy direction in σ8 − Ωm space; we find consistency with the lensing results from the Dark Energy Survey, and give combined lensing-only parameter constraints that are tighter than joint results using galaxy clustering. Using the Planck cosmic infrared background (CIB) maps as an additional tracer of high-redshift matter, we make a combined Planck-only estimate of the lensing potential over 60% of the sky with considerably more small-scale signal. We additionally demonstrate delensing of the Planck power spectra using the joint and individual lensing potential estimates, detecting a maximum removal of 40% of the lensing-induced power in all spectra. The improvement in the sharpening of the acoustic peaks by including both CIB and the quadratic lensing reconstruction is detected at high significance.

scholarly journals Constraining cosmology with the cosmic microwave and infrared backgrounds correlation

2019 ◽  
Vol 621 ◽  
pp. A32 ◽  
Author(s):  
A. Maniyar ◽  
G. Lagache ◽  
M. Béthermin ◽  
S. Ilić
Keyword(s):  
Large Scale ◽  
Cross Correlation ◽  
Signal To Noise Ratio ◽  
Cosmological Parameters ◽  
Power Spectra ◽  
Matrix Analysis ◽  
Microwave Background ◽  
Residual Level ◽  
Infrared Background ◽  
The Cross

We explore the use of the cosmic infrared background (CIB) as a tracer of the large scale structures for cross-correlating with the cosmic microwave background (CMB) and exploit the integrated Sachs–Wolfe (ISW) effect. We used an improved linear CIB model from our previous work and derived the theoretical CIB×ISW cross-correlation for different Planck HFI frequencies (217, 353, 545 and 857 GHz) and IRAS (3000 GHz). As expected, we predict a positive cross-correlation between the CIB and the CMB whose amplitude decreases rapidly at small scales. We perform a signal-to-noise ratio (S/N) analysis of the predicted cross-correlation. In the ideal case when the cross-correlation is obtained over 70% (40%) of the sky without residual contaminants (e.g. galactic dust) in maps, the S/N ranges from 4.2 to 5.6 (3.2 to 4.3); the highest S/N comes from 857 GHz. A Fisher matrix analysis shows that an ISW signal detected with a S/N this high on the 40% sky can considerably improve the constraints on the cosmological parameters; constraints on the equation of state of the dark energy especially are improved by 80%. We then performed a more realistic analysis considering the effect of residual galactic dust contamination in CIB maps. We calculated the dust power spectra for different frequencies and sky fractions that dominate the CIB power spectra at the lower multipoles we are interested in. Considering a conservative 10% residual level of galactic dust in the CIB power spectra, we observe that the S/N drops drastically, which makes it very challenging to detect the ISW. To determine the capability of current maps to detect the ISW effect through this method, we measured the cross-correlation of the CIB and the CMB Planck maps on the so-called GASS field, which covers an area of ∼11% in the southern hemisphere. We find that with such a small sky fraction and the dust residuals in the CIB maps, we do not detect any ISW signal, and the measured cross-correlation is consistent with zero. To avoid degrading the S/N for the ISW measurement by more than 10% on the 40% sky, we find that the dust needs to be cleaned up to the 0.01% level on the power spectrum.

Polarity Change Extraction of GPR Data for Under-road Cavity Detection: Application on Sudeoksa Testbed Data

2019 ◽  
Vol 24 (3) ◽  
pp. 419-431
Author(s):  
Jongha Hwang ◽  
Donggeon Kim ◽  
Xiangyue Li ◽  
Dong-Joo Min
Keyword(s):  
Phase Shift ◽  
Power Spectrum ◽  
Cross Correlation ◽  
Survey Methods ◽  
Time Lag ◽  
Background Signal ◽  
Data Set ◽  
Air Ground Interface ◽  
The Cross ◽  
Polarity Change

Ground penetrating radar (GPR) is one of the most widely used geophysical survey methods to locate cavities under roads due to its speedy exploration and high-resolution imaging. To locate underground cavities using GPR, we need to distinguish between cavity-induced reflections and other reflections, which can be achieved by examining the polarity change in reflections compared to the polarity of the transmitted signal. The polarity change can be measured from the phase shift between the target and first reflections. To estimate the phase shift in reflections, the method of computing the power spectrum difference between the original trace and background signal was proposed, but the method has a limitation for shallow reflectors. As an alternative method to avoid this limitation, we propose using only one component of the power spectrum difference, the cross-correlation between the target reflection and background signal. The cross-correlation has its maximum peak at a time lag between the target and first reflection (from the air-ground interface). Additionally, the phase at that time lag represents a phase shift between the two reflections. We compare our cross-correlation-based method with the conventional method of computing the whole power spectrum difference and investigate the feasibility of our method for distinguishing cavity-induced reflections using a 2D field data set acquired in a testbed in Sudeoksa, Korea.

scholarly journals First measurement of the cross-correlation between CMB weak lensing and X-ray emission

2019 ◽  
Vol 625 ◽  
pp. L4 ◽  
Author(s):  
G. Hurier ◽  
P. Singh ◽  
C. Hernández-Monteagudo
Keyword(s):  
Cross Correlation ◽  
Power Spectra ◽  
Galaxy Cluster ◽  
Weak Lensing ◽  
X Rays ◽  
Satellite Mission ◽  
Local Universe ◽  
Best Fitting ◽  
The Cross ◽  
Hydrodynamical Simulations

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.

scholarly journals Variations of the Low l Solar Acoustic Spectrum Correlated with the Activity Cycle

1990 ◽  
Vol 121 ◽  
pp. 349-355 ◽  
Author(s):  
P.L. Pallé ◽  
C. Régulo ◽  
T. Roca Cortés
Keyword(s):  
Solar Activity ◽  
Solar Cycle ◽  
Cross Correlation ◽  
Power Spectra ◽  
Activity Cycle ◽  
Solar Activity Cycle ◽  
Frequency Variation ◽  
Acoustic Oscillations ◽  
Solar Cycle Variation ◽  
The Cross

AbstractSolar cycle variation of the frequencies and of the power of solar acoustic oscillations are investigated. Integrated sunlight data from 1977 to 1988 obtained at the Observatorio del Teide (Izaña, Tenerife), using a resonant scattering spectrophotometer, is analyzed in 60 day time strings and their power spectra are calculated from 2 to 3.8 mHz. To study the frequency variation, each power spectrum is cross-correlated with the one corresponding to the 1981 series and the shifts of the centroids of the cross-correlation peaks are calculated. The results show a clear variation in frequency of the cross-correlation peaks of −0.37 ± 0.04 μHz peak to peak as solar activity cycle goes from maximum to minimum. Moreover, this effect is found to depend on the l value of the modes, being absent for l = 0 and of 0.42 ± 0.06 μHz for l = 1. These results can be interpreted as an amplitude modulation between modes of the same multiplet, probably as a consequence of the action of strong magnetic fields. As low l modes penetrate deeply into the Sun’s interior, these observations suggest changes in its structure correlated with the solar activity cycle. When the power of the modes is calculated, using the same series as before, and its change along the solar cycle is studied, a variation of ~ 40% is found, the power being higher when solar activity is at its minimum. If this effect is independent of the l value of the p-modes, the results can be interpreted in terms of a change in the efficiency of the excitation mechanism of such modes. Indeed, if turbulent convection is such a mechanism, a change in the characteristic size of the granulation would account for the observed effect. Alternatively, another explanation could be a selective change in the efficiency of the excitation and/or damping mechanisms of the l ≤ 3 modes in front of other l value modes.

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