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Detection of the ISW and SZ effects from the CMB-Galaxy correlation

Pablo Fosalba, Enrique Gaztanaga, Francisco Castander

TL;DR

This workCross-correlates WMAP CMB temperature maps with SDSS DR1 galaxy densities to detect ISW and SZ imprints. It uses JK resampling and MC simulations to robustly estimate errors, finding significant cross-correlations for both low- and high-redshift galaxy samples. The ISW signal on large angular scales and the SZ signal on small scales are jointly analyzed against ΛCDM predictions, yielding a best-fit Ω_Λ≈0.8 with 2σ bounds ~0.69–0.86 and a Compton parameter mean of y≈1.3×10^-6. These results bolster the presence of dark energy and demonstrate a pathway to characterize intracluster gas via CMB–galaxy correlations.

Abstract

We present a cross-correlation analysis of the WMAP cosmic microwave background (CMB) temperature anisotropies and the SDSS galaxy density fluctuations. We find significant detections of the angular CMB-galaxy correlation for both the flux limited galaxy sample (z~0.3) and the high redshift (z ~ 0.5) color selected sample. The signal is compatible with that expected from the integrated Sachs-Wolfe (ISW) effect at large angles (θ> 3deg) and the Sunyaev-Zeldovich (SZ) effect at small scales (θ< 1 deg). The detected correlation at low-z is in good agreement with a previous analysis using the APM survey (z~0.15). The combined analysis of all 3 samples yields a total significance better than 3 sigma for ISW and about 2.7 σfor SZ, with a Compton parameter y~10^(-6). For a given flat LCDM model, the ISW effect depends both on the value of Ω_Λand the galaxy bias b. To break this degeneracy, we estimate the bias using the ratio between the galaxy and mass auto-correlation functions in each sample. With our bias estimation, all samples consistently favor a best fit dark-energy dominated model: Ω_Λ~ 0.8, with a 2 σerror Ω_Λ=0.69-0.86.

Detection of the ISW and SZ effects from the CMB-Galaxy correlation

TL;DR

This workCross-correlates WMAP CMB temperature maps with SDSS DR1 galaxy densities to detect ISW and SZ imprints. It uses JK resampling and MC simulations to robustly estimate errors, finding significant cross-correlations for both low- and high-redshift galaxy samples. The ISW signal on large angular scales and the SZ signal on small scales are jointly analyzed against ΛCDM predictions, yielding a best-fit Ω_Λ≈0.8 with 2σ bounds ~0.69–0.86 and a Compton parameter mean of y≈1.3×10^-6. These results bolster the presence of dark energy and demonstrate a pathway to characterize intracluster gas via CMB–galaxy correlations.

Abstract

We present a cross-correlation analysis of the WMAP cosmic microwave background (CMB) temperature anisotropies and the SDSS galaxy density fluctuations. We find significant detections of the angular CMB-galaxy correlation for both the flux limited galaxy sample (z~0.3) and the high redshift (z ~ 0.5) color selected sample. The signal is compatible with that expected from the integrated Sachs-Wolfe (ISW) effect at large angles (θ> 3deg) and the Sunyaev-Zeldovich (SZ) effect at small scales (θ< 1 deg). The detected correlation at low-z is in good agreement with a previous analysis using the APM survey (z~0.15). The combined analysis of all 3 samples yields a total significance better than 3 sigma for ISW and about 2.7 σfor SZ, with a Compton parameter y~10^(-6). For a given flat LCDM model, the ISW effect depends both on the value of Ω_Λand the galaxy bias b. To break this degeneracy, we estimate the bias using the ratio between the galaxy and mass auto-correlation functions in each sample. With our bias estimation, all samples consistently favor a best fit dark-energy dominated model: Ω_Λ~ 0.8, with a 2 σerror Ω_Λ=0.69-0.86.

Paper Structure

This paper contains 6 sections, 2 equations, 4 figures.

Table of Contents

  1. Introduction
  2. Data
  3. Cross-Correlation and Statistical tests
  4. Comparison to Predictions
  5. Significance tests
  6. Discussion

Figures (4)

  • Figure 1: Errors in the cross-correlation $w_{TG}(\theta)$ from the dispersion in 200 Monte-Carlo simulations (solid line) as compared with the mean and dispersion (squares with errobars) in the Jack-knife (JK) error estimation over the same simulations. Dashed line correspond to the JK error in the real WMAP- SDSS all sample.
  • Figure 2: WMAP-SDSS correlation: long dashed-line shows the measurement for the SDSS HIGH-Z sample, while the solid line displays the correlation for the SDSS ALL sample. For reference, short-dashed line displays the same measurement using the APM galaxy survey instead of SDSS. Boxes show 1-$\sigma$ error-bars.
  • Figure 3: Theoretical predictions: (Bottom panel) Continuous, long and short dashed lines show the ISW, SZ and lensing predictions. Different sets of lines correspond to the APM (black), SDSS all (red) and SDSS high-z (blue) samples. (Top panel) The total prediction (ISW+SZ+Lensing) for the 3 samples. We have assumed a $\Lambda$CDM model with a fixed $b_{gas}=2$ in all cases, $b=3$ for SDSS high-z and $b=1$ for APM and SDSS all.
  • Figure 4: Estimating dark-energy: Long-dashed, short-dashed and dot-dashed lines show the probability distribution for $\Omega_\Lambda$ in the SDSS all, APM and SDSS high-z samples. The combined distribution (for 3 d.o.f.) is shown by the solid line.