Kinematic Sunyaev-Zel’dovich Effect with Projected Fields: A Novel Probe of the Baryon Distribution with Planck, WMAP, and WISE Data

Abstract

The kinematic Sunyaev-Zel'dovich (KSZ) effect-the Doppler boosting of cosmic microwave background (CMB) photons due to Compton scattering off free electrons with nonzero bulk velocity-probes the abundance and the distribution of baryons in the Universe. All KSZ measurements to date have explicitly required spectroscopic redshifts. Here, we implement a novel estimator for the KSZ-large-scale structure cross-correlation based on projected fields: it does not require redshift estimates for individual objects, allowing KSZ measurements from large-scale imaging surveys. We apply this estimator to cleaned CMB temperature maps constructed from Planck and WMAP data and a galaxy sample from the Wide-field Infrared Survey Explorer (WISE). We measure the KSZ effect at 3.8σ-4.5σ significance, depending on the use of additional WISE galaxy bias constraints. We verify that our measurements are robust to possible dust emission from the WISE galaxies. Assuming the standard Λ cold dark matter cosmology, we directly constrain (f_{b}/0.158)(f_{free}/1.0)=1.48±0.19 (statistical error only) at redshift z≈0.4, where f_{b} is the fraction of matter in baryonic form and f_{free} is the free electron fraction. This is the tightest KSZ-derived constraint reported to date on these parameters. Astronomers have long known that baryons do not trace dark matter on ∼ kiloparsec scales and there has been strong evidence that galaxies are baryon poor. The consistency between the f_{b} value found here and the values inferred from analyses of the primordial CMB and big bang nucleosynthesis verifies that baryons approximately trace the dark matter distribution down to ∼ megaparsec scales. While our projected-field estimator is already competitive with other KSZ approaches when applied to current data sets (because we are able to use the full-sky WISE photometric survey), it will yield enormous signal-to-noise ratios when applied to upcoming high-resolution, multifrequency CMB surveys.

Reconstructing cosmic growth with kinetic Sunyaev-Zel’dovich observations in the era of stage IV experiments

“…This reduces the measurement uncertainties, and extends the mass range of the resulting cluster sample to smaller masses (although, for a fixed lower mass bound, the method will be limited by the number of haloes present in the surveyed patch, which is a different manifestation of the cosmic variance problem). This very fact also distinguishes this method from other procedures proposed in the literature to measure the kSZ effect, such as the pairwise kSZ signal [73] or the projected-field probe of [20]. These methods would in turn be less sensitive to cluster blending effects.…”

“…The potential of combining kSZ measurements with galaxy surveys has been discussed before: forecasts for combinations of upcoming experiments were explored in [23,[27][28][29], and redshift surveys were essential in the first determination of the kSZ streaming velocity [16], as well as more recent attempts using the CMASS survey to pull out the kSZ signal at redshifts z ∼ 0.4-0.7 [18]. In this section we build on previous work and lay out, in detail, the observables that we need to work with, and the various steps involved in building up a reliable estimator for the growth rate.…”

“…The kSZ effect has already been detected statistically, arguably using the WMAP data [15], but most decisively with data from ACT, [16], Planck [17], ACTPol [18], and SPT [19], as well as the combined measurement of [20]. Pointed (i.e.…”

Multitracer CMB delensing maps from Planck and WISE data

“…The cross-correlation coefficient can reach values as high as ρ ≈ 70%, depending on the CIB frequency and angular scales considered. The distribution of infrared galaxies probed by WISE has also been shown to be well-correlated with the CMB lensing potential [33]. Although the WISE galaxy density map has a lower overall cross-correlation coefficient with the CMB lensing field (ρ ≈ 30%) than the CIB does, its redshift kernel is highly complementary to that of the CIB (see Fig.…”

“…WISE mapped the entire sky at wavelengths of 3.4, 4.6, 12, and 22 µm with an angular resolution of 6.1 , 6.4 , 6.5 , and 12.0 , respectively [41]. In particular, we use a WISE galaxy sample constructed via color cuts (following [42]) for analyses of the integrated Sachs-Wolfe [43] and kinematic SunyaevZel'dovich effects [33,44]. Although these galaxies are located at relatively low redshift (z < 1, with a peak at z ≈ 0.3 [45]), their cross-correlation with the Planck PR2 CMB lensing map has been detected at 56σ [33].…”