Evidence for an extended Sunyaev--Zel'dovich effect in WMAP data

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.

Detection of the Integrated Sachs-Wolfe and Sunyaev-Zeldovich Effects from the Cosmic Microwave Background-Galaxy Correlation

“…The ISW detection is in agreement with other analyses based on X-ray and radio sources (Boughn & Crittenden 2003;Nolta et al 2003), while Hernandez-Monteagudo & Rubino-Martin (2003) fail to detect the SZ effect when comparing WMAP with different optical cluster templates (see also Myers et al 2003). It should be stressed nevertheless that cluster or galaxy group catalogs are too sparse and typically produce worse signal-to-noise ratios than galaxy surveys.…”

The Search for the Missing Baryons at Low Redshift

“…Hernández-Monteagudo et al (2004) searched for but failed to see a S-Z signal from structures less bound than clusters. Myers et al (2004) report on a similar study that used the same WMAP data in which they have a marginal detection of the S-Z effect on a size scale (5 Mpc) somewhat greater than the virial radius of the cluster. Given the disagreement between the groups and the marginal detection by Myers et al (2004), the evidence is not compelling that the S-Z effect has been detected beyond the virial radius of galaxy clusters.…”

Three‐YearWilkinson Microwave Anisotropy Probe(WMAP) Observations: Temperature Analysis

“…In our first-year analysis we reported detections of an SZ signal from the Coma cluster and from an aggregate sample of X-ray-selected Abell clusters, the XBAC catalog. Since then, there have been numerous additional reports of SZ signal detection in the first-year WMAP data (Fosalba & Gaztañaga 2004;Fosalba et al 2003;Myers et al 2004;Afshordi et al 2004Afshordi et al , 2005Hernández-Monteagudo & Rubiño-Martín 2004;Hansen et al 2005;Atrio-Barandela & Muecket 2006). In this section, we update our results for the Coma cluster and the XBAC catalog; in subsequent cosmological studies, we mask these clusters from the data.…”