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Chandra Shekhar Saraf
Publication date
2021
fields
Physics
and research's language is
English
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We present the first study of cross-correlation between Cosmic Microwave Background (CMB) gravitational lensing potential map measured by the $Planck$ satellite and $zgeq 0.8$ galaxies from the photometric redshift catalogues from Herschel Extragalactic Legacy Project (HELP), divided into four sky patches: NGP, Herschel Stripe-82 and two halves of SGP field, covering in total $sim 660$ deg$^{2}$ of the sky. Contrary to previous studies exploiting only the common area between galaxy surveys and CMB lensing data, we improve the cross-correlation measurements using the full available area of the CMB lensing map. We estimate galaxy linear bias parameter, $b$, from joint analysis of cross-power spectrum and galaxy auto-power spectrum using Maximum Likelihood Estimation technique to obtain the value averaged over four fields as $b=2.06_{-0.02}^{+0.02}$, ranging from $1.94_{-0.03}^{+0.04}$ for SGP Part-2 to $3.03_{-0.09}^{+0.10}$ for NGP. We also estimate the amplitude of cross-correlation and find the averaged value to be $A=0.52_{-0.08}^{+0.08}$ spanning from $0.34_{-0.19}^{+0.19}$ for NGP to $0.67_{-0.20}^{+0.21}$ for SGP Part-1 respectively, significantly lower than expected value for the standard cosmological model. We perform several tests on systematic errors that can account for this discrepancy. We find that lower amplitude could be to some extent explained by the lower value of median redshift of the catalogue, however, we do not have any evidence that redshifts are systematically overestimated.
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Cosmic Microwave Background (CMB) is a powerful probe to study the early universe and various cosmological models. Weak gravitational lensing affects the CMB by changing its power spectrum, but meanwhile, it also carries information about the distribution of lensing mass and hence, the large scale structure (LSS) of the universe. When studies of the CMB is combined with the tracers of LSS, one can constrain cosmological models, models of LSS development and astrophysical parameters simultaneously. The main focus of this project is to study the cross-correlations between CMB lensing and the galaxy matter density to constrain the galaxy bias ($b$) and the amplitude scaling parameter ($A$), to test the validity of $Lambda$CDM model. We test our approach for simulations of the Planck CMB convergence field and galaxy density field, which mimics the density field of the Herschel Extragalactic Legacy Project (HELP). We use maximum likelihood method to constrain the parameters.
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$sigma$.
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 the first measurement of the correlation between the map of the cosmic microwave background (CMB) lensing potential derived from the emph{Planck} nominal mission data and $zgtrsim 1.5$ galaxies detected by the emph{Herschel}-ATLAS (H-ATLAS) survey covering about $600,hbox{deg}^2$, i.e. about 1.4% of the sky. We reject the hypothesis that there is no correlation between CMB lensing and galaxy detection at a $20,sigma$ significance, checking the result by performing a number of null tests. The significance of the detection of the theoretically expected cross-correlation signal is found to be $10,sigma$. The galaxy bias parameter, $b$, derived from a joint analysis of the cross-power spectrum and of the auto-power spectrum of the galaxy density contrast is found to be $b=2.80^{+0.12}_{-0.11}$, consistent with earlier estimates for H-ATLAS galaxies at similar redshifts. On the other hand, the amplitude of the cross-correlation is found to be a factor $1.62 pm 0.16$ higher than expected from the standard model and also found by cross-correlation analyses with other tracers of the large-scale structure. The enhancement due to lensing magnification can account for only a fraction of the excess cross-correlation signal. We suggest that part of it may be due to an incomplete removal of the contamination of the CIB, that includes the H-ATLAS sources we are cross-correlating with. In any case, the highly significant detection reported here using a catalog covering only 1.4% of the sky demonstrates the potential of CMB lensing correlations with submillimeter surveys.
We cross-correlate galaxy weak lensing measurements from the Dark Energy Survey (DES) year-one (Y1) data with a cosmic microwave background (CMB) weak lensing map derived from South Pole Telescope (SPT) and Planck data, with an effective overlapping area of 1289 deg$^{2}$. With the combined measurements from four source galaxy redshift bins, we reject the hypothesis of no lensing with a significance of $10.8sigma$. When employing angular scale cuts, this significance is reduced to $6.8sigma$, which remains the highest signal-to-noise measurement of its kind to date. We fit the amplitude of the correlation functions while fixing the cosmological parameters to a fiducial $Lambda$CDM model, finding $A = 0.99 pm 0.17$. We additionally use the correlation function measurements to constrain shear calibration bias, obtaining constraints that are consistent with previous DES analyses. Finally, when performing a cosmological analysis under the $Lambda$CDM model, we obtain the marginalized constraints of $Omega_{rm m}=0.261^{+0.070}_{-0.051}$ and $S_{8}equiv sigma_{8}sqrt{Omega_{rm m}/0.3} = 0.660^{+0.085}_{-0.100}$. These measurements are used in a companion work that presents cosmological constraints from the joint analysis of two-point functions among galaxies, galaxy shears, and CMB lensing using DES, SPT and Planck data.
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