Article

# On the presence of thermal Sunyaev-Zel'dovich induced signal in the first-year WMAP temperature maps

Monthly Notices of the Royal Astronomical Society (Impact Factor: 5.11). 01/2004; 347(2):403-410. DOI: 10.1111/j.1365-2966.2004.07205.x

Source: arXiv

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**ABSTRACT:**We present results from a test for the Gaussianity of the whole sky sub-degree scale CMB temperature anisotropy measured by the Wilkinson Microwave Anisotropy Probe (WMAP). We calculate the genus from the foreground-subtracted and Kp0-masked WMAP maps and measure the genus shift parameters defined at negative and positive threshold levels and the asymmetry parameter to quantify the deviation from the Gaussian relation. At WMAP Q, V, and W bands, the genus and genus-related statistics imply that the observed CMB sky is consistent with Gaussian random phase field. However, from the genus measurement on the Galactic northern and southern hemispheres, we have found two non-Gaussian signatures at the W band resolution (0.35 degree scale), i.e., the large difference of genus amplitudes between the north and the south and the positive genus asymmetry in the south, which are statistically significant at 2.6 sigma and 2.4 sigma levels, respectively. The large genus amplitude difference also appears in the WMAP Q and V band maps, deviating the Gaussian prediction with a significance level of about 2 sigma. The probability that the genus curves show such a large genus amplitude difference exceeding the observed values at all Q, V, and W bands in a Gaussian sky is only 1.4%. Such non-Gaussian features are reduced as the higher Galactic cut is applied, but their dependence on the Galactic cut is weak. We discuss possible sources that can induce such non-Gaussian features, and conclude that the CMB data with higher signal-to-noise ratio and the accurate foreground model are needed to understand the non-Gaussian signatures. Comment: 9 pages, 5 figures, MNRAS in press (citation error corrected) - [Show abstract] [Hide abstract]

**ABSTRACT:**We present results for the cross-correlation between the WMAP 1st-year cosmic microwave background (CMB) anisotropy data and optical galaxy surveys: the APM and SDSS DR1 catalogs. Our measurement of a positive CMB-galaxy correlation on large angles (\theta > 4 deg) yields significant detections of the Integrated Sachs-Wolfe (ISW) effect and provides a new estimate of dark-energy in the universe, \Omega_\Lambda=0.69-0.86 (2 \sigma range). In addition, the correlated signal on small angles (\theta<1 deg) reveals the imprint left by hot intra-cluster gas in the CMB photons: the thermal Sunyaev-Zeldovich (SZ) effect - [Show abstract] [Hide abstract]

**ABSTRACT:**We have cross-correlated the WMAP data with several surveys of extragalactic sources and find evidence for temperature decrements associated with galaxy clusters and groups detected in the APM Galaxy Survey and the Abell–Corwin–Olowin (ACO) catalogue. We interpret this as evidence for the thermal Sunyaev–Zel'dovich (SZ) effect from the clusters. Most interestingly, the signal may extend to ≈ 1 deg (≈5 h−1 Mpc) around both groups and clusters and we suggest that this may be due to hot ‘supercluster’ gas. We have further cross-correlated the WMAP data with clusters identified in the 2MASS galaxy catalogue and also find evidence for temperature decrements there. From the APM group data we estimate the mean Compton parameter as y(z < 0.2) = 7 ± 3.8 × 10−7. We have further estimated the gas mass associated with the galaxy group and cluster haloes. Assuming temperatures of 5 keV for ACO clusters and 1 keV for APM groups and clusters, we derive average gas masses of M(r < 1.75 h−1 Mpc) ≈ 3 × 1013h−2 M⊙ for both, the assumed gas temperature and SZ central decrement differences approximately cancelling. Using the space density of APM groups we then estimate Ωgas0≈ 0.03 h−1 (1 keV/kT)(θmax/20 arcmin)0.75. For an SZ extent of θmax= 20 arcmin, kT= 1 keV and h= 0.7, this value of Ωgas0≈ 0.04 is consistent with the standard value of Ωbaryon0= 0.044, but if the indications we have found for a more extended SZ effect out to θmax≈ 60 arcmin are confirmed, then higher values of Ωgas0 will be implied. Finally, the contribution to the WMAP temperature power spectrum from the extended SZ effect around the z < 0.2 APM+ACO groups and clusters is 1–2 orders of magnitude lower than the l= 220 first acoustic peak. But if a similar SZ effect arises from more distant clusters then this contribution could increase by a factor >10 and then could seriously affect the WMAP cosmological fits.