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Register a new userKiDS-450: Tomographic Cross-Correlation of Galaxy Shear with {it Planck} Lensing
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Added by
Joachim Harnois-Deraps
Publication date
2017
fields
Physics
and research's language is
English
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We present the tomographic cross-correlation between galaxy lensing measured in the Kilo Degree Survey (KiDS-450) with overlapping lensing measurements of the cosmic microwave background (CMB), as detected by Planck 2015. We compare our joint probe measurement to the theoretical expectation for a flat $Lambda$CDM cosmology, assuming the best-fitting cosmological parameters from the KiDS-450 cosmic shear and Planck CMB analyses. We find that our results are consistent within $1sigma$ with the KiDS-450 cosmology, with an amplitude re-scaling parameter $A_{rm KiDS} = 0.86 pm 0.19$. Adopting a Planck cosmology, we find our results are consistent within $2sigma$, with $A_{it Planck} = 0.68 pm 0.15$. We show that the agreement is improved in both cases when the contamination to the signal by intrinsic galaxy alignments is accounted for, increasing $A$ by $sim 0.1$. This is the first tomographic analysis of the galaxy lensing -- CMB lensing cross-correlation signal, and is based on five photometric redshift bins. We use this measurement as an independent validation of the multiplicative shear calibration and of the calibrated source redshift distribution at high redshifts. We find that constraints on these two quantities are strongly correlated when obtained from this technique, which should therefore not be considered as a stand-alone competitive calibration tool.
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We present cosmological parameter constraints from a tomographic weak gravitational lensing analysis of ~450deg$^2$ of imaging data from the Kilo Degree Survey (KiDS). For a flat $Lambda$CDM cosmology with a prior on $H_0$ that encompasses the most recent direct measurements, we find $S_8equivsigma_8sqrt{Omega_{rm m}/0.3}=0.745pm0.039$. This result is in good agreement with other low redshift probes of large scale structure, including recent cosmic shear results, along with pre-Planck cosmic microwave background constraints. A $2.3$-$sigma$ tension in $S_8$ and `substantial discordance in the full parameter space is found with respect to the Planck 2015 results. We use shear measurements for nearly 15 million galaxies, determined with a new improved `self-calibrating version of $lens$fit validated using an extensive suite of image simulations. Four-band $ugri$ photometric redshifts are calibrated directly with deep spectroscopic surveys. The redshift calibration is confirmed using two independent techniques based on angular cross-correlations and the properties of the photometric redshift probability distributions. Our covariance matrix is determined using an analytical approach, verified numerically with large mock galaxy catalogues. We account for uncertainties in the modelling of intrinsic galaxy alignments and the impact of baryon feedback on the shape of the non-linear matter power spectrum, in addition to the small residual uncertainties in the shear and redshift calibration. The cosmology analysis was performed blind. Our high-level data products, including shear correlation functions, covariance matrices, redshift distributions, and Monte Carlo Markov Chains are available at http://kids.strw.leidenuniv.nl.
We measure the cross-correlation between galaxy groups constructed from DESI Legacy Imaging Survey DR8 and Planck CMB lensing, over overlapping sky area of 16876 $rm deg^2$. The detections are significant and consistent with the expected signal of the large scale structure of the universe, over group samples of various redshift, mass and richness $N_{rm g}$ and over various scale cuts. The overall S/N is 39 for a conservative sample with $N_{rm g}geq 5$, and increases to $48$ for the sample with $N_{rm g}geq 2$. Adopting the Planck 2018 cosmology, we constrain the density bias of groups with $N_{rm g}geq 5$ as $b_{rm g}=1.31pm 0.10$, $2.22pm 0.10$, $3.52pm 0.20$ at $0.1<zleq 0.33$, $0.33<zleq 0.67$, $0.67<zleq1$ respectively. The value-added group catalog allows us to detect the dependence of bias on group mass with high significance. It also allows us to compare the measured bias with the theoretically predicted one using the estimated group mass. We find excellent agreement for the two high redshift bins. However, it is lower than the theory by $sim 3sigma$ for the lowest redshift bin. Another interesting finding is the significant impact of the thermal Sunyaev Zeldovich (tSZ). It contaminates the galaxy group-CMB lensing cross-correlation at $sim 30%$ level, and must be deprojected first in CMB lensing reconstruction.
We present measurements of the weak gravitational lensing shear power spectrum based on $450$ sq. deg. of imaging data from the Kilo Degree Survey. We employ a quadratic estimator in two and three redshift bins and extract band powers of redshift auto-correlation and cross-correlation spectra in the multipole range $76 leq ell leq 1310$. The cosmological interpretation of the measured shear power spectra is performed in a Bayesian framework assuming a $Lambda$CDM model with spatially flat geometry, while accounting for small residual uncertainties in the shear calibration and redshift distributions as well as marginalising over intrinsic alignments, baryon feedback and an excess-noise power model. Moreover, massive neutrinos are included in the modelling. The cosmological main result is expressed in terms of the parameter combination $S_8 equiv sigma_8 sqrt{Omega_{rm m}/0.3}$ yielding $S_8 = 0.651 pm 0.058$ (3 z-bins), confirming the recently reported tension in this parameter with constraints from Planck at $3.2sigma$ (3 z-bins). We cross-check the results of the 3 z-bin analysis with the weaker constraints from the 2 z-bin analysis and find them to be consistent. The high-level data products of this analysis, such as the band power measurements, covariance matrices, redshift distributions, and likelihood evaluation chains are available at http://kids.strw.leidenuniv.nl/
We present a tomographic cosmic shear analysis of the Kilo-Degree Survey (KiDS) combined with the VISTA Kilo-Degree Infrared Galaxy Survey (VIKING). This is the first time that a full optical to near-infrared data set has been used for a wide-field cosmological weak lensing experiment. This unprecedented data, spanning $450~$deg$^2$, allows us to improve significantly the estimation of photometric redshifts, such that we are able to include robustly higher-redshift sources for the lensing measurement, and - most importantly - solidify our knowledge of the redshift distributions of the sources. Based on a flat $Lambda$CDM model we find $S_8equivsigma_8sqrt{Omega_{rm m}/0.3}=0.737_{-0.036}^{+0.040}$ in a blind analysis from cosmic shear alone. The tension between KiDS cosmic shear and the Planck-Legacy CMB measurements remains in this systematically more robust analysis, with $S_8$ differing by $2.3sigma$. This result is insensitive to changes in the priors on nuisance parameters for intrinsic alignment, baryon feedback, and neutrino mass. KiDS shear measurements are calibrated with a new, more realistic set of image simulations and no significant B-modes are detected in the survey, indicating that systematic errors are under control. When calibrating our redshift distributions by assuming the 30-band COSMOS-2015 photometric redshifts are correct (following the Dark Energy Survey and the Hyper Suprime-Cam Survey), we find the tension with Planck is alleviated. The robust determination of source redshift distributions remains one of the most challenging aspects for future cosmic shear surveys.
We present an improved and extended analysis of the cross-correlation between the map of the Cosmic Microwave Background (CMB) lensing potential derived from the emph{Planck} mission data and the high-redshift galaxies detected by the emph{Herschel} Astrophysical Terahertz Large Area Survey (H-ATLAS) in the photometric redshift range $z_{rm ph} ge 1.5$. We compare the results based on the 2013 and 2015 textit{Planck} datasets, and investigate the impact of different selections of the H-ATLAS galaxy samples. Significant improvements over our previous analysis have been achieved thanks to the higher signal-to-noise ratio of the new CMB lensing map recently released by the textit{Planck} collaboration. The effective galaxy bias parameter, $b$, for the full galaxy sample, derived from a joint analysis of the cross-power spectrum and of the galaxy auto-power spectrum is found to be $b = 3.54^{+0.15}_{-0.14}$. Furthermore, a first tomographic analysis of the cross-correlation signal is implemented, by splitting the galaxy sample into two redshift intervals: $1.5 le z_{rm ph} < 2.1$ and $z_{rm ph}ge 2.1$. A statistically significant signal was found for both bins, indicating a substantial increase with redshift of the bias parameter: $b=2.89pm0.23$ for the lower and $b=4.75^{+0.24}_{-0.25}$ for the higher redshift bin. Consistently with our previous analysis we find that the amplitude of the cross correlation signal is a factor of $1.45^{+0.14}_{-0.13}$ higher than expected from the standard $Lambda$CDM model for the assumed redshift distribution. The robustness of our results against possible systematic effects has been extensively discussed although the tension is mitigated by passing from 4 to 3$sigma$.
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