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

Abstract

Future ground-based cosmic microwave background (CMB) experiments will generate competitive large-scale structure data sets by precisely characterizing CMB secondary anisotropies over a large fraction of the sky. We describe a method for constraining the growth rate of structure to sub-1% precision out to z ≈ 1, using a combination of galaxy cluster peculiar velocities measured using the kinetic SunyaevZel'dovich (kSZ) effect, and the velocity field reconstructed from galaxy redshift surveys. We consider only thermal SZ-selected cluster samples, which will consist of Oð10 4 -10 5 Þ sources for Stage 3 and 4 CMB experiments respectively. Three different methods for separating the kSZ effect from the primary CMB are compared, including a novel blind "constrained realization" method that improves signal-to-noise by a factor of ∼2 over a commonly-used aperture photometry technique. Assuming a correlation between the integrated tSZ y-parameter and the cluster optical depth, it should then be possible to break the kSZ velocity-optical depth degeneracy. The effects of including CMB polarization and SZ profile uncertainties are also considered. In the absence of systematics, a combination of future Stage 4 experiments should be able to measure the product of the growth and expansion rates, α ≡ fH, to better than 1% in bins of Δz ¼ 0.1 out to z ≈ 1-competitive with contemporary redshift-space distortion constraints from galaxy surveys. We conclude with a discussion of the likely impact of various systematics.

Constraints on the Optical Depth of Galaxy Groups and Clusters

“…Here, we highlight a few illustrative examples from the recent literature. Alonso et al (2016) show that, with data from Stage IV experiments, it would be possible to measure the product of the Hubble rate and the growth rate, f z H z ( ) ( ), to better than 1% out to z=1 with the redshift bins of z 0.1 D = . However, their conclusion hinges on the assumption that we will have precise knowledge of the optical depth, which, they argue, can be obtained using the scaling relation between the integrated tSZ y-parameter and τ.…”

“…From a cosmological perspective, measurements of the kSZ effect have the potential of probing dark energy and modified gravity (DeDeo et al 2005;Hernandez-Monteagudo et al 2006;Bhattacharya & Kosowsky 2008;Kosowsky & Bhattacharya 2009;Keisler & Schmidt 2013;Ma & Zhao 2014;Mueller et al 2015;Alonso et al 2016), as well as the sum of the neutrino masses (Mueller et al 2014). However, the constraining power of the kSZ signal is fundamentally limited by our understanding of the integrated electron density, i.e., the optical depth, of the galaxy clusters sourcing the signal.…”

Bias to CMB lensing reconstruction from temperature anisotropies due to large-scale galaxy motions

“…Taking advantage of this sensitivity to the gas distribution, recent detections of the kSZ signal have made progress towards resolving the long-standing "missing baryons" problem at low redshift [14,30,31,51,52]. In addition, through its dependence on the large-scale velocity field, the kSZ effect can also be used as a cosmological probe to measure the growth of structure [53][54][55]. In this paper, however, we will focus on the bias it imprints on CMB lensing reconstruction.…”

Measuring polarized emission in clusters in the CMB S4 era

“…n T , n Q and n U represent the instrumental noise in temperature and polarization data, with σ(n Q ) = σ(n U ) = √ 2σ(n T ). A derivation of the matched filter for the tSZ emission can be found in [15]. The maximum-likelihood solution for the tSZ amplitude is given by…”

“…We follow [15] and compute the cluster detection efficiencỹ Here P SZ accounts for the intrinsic scatter in the relationship between tSZ flux and mass (e.g [15]). P det quantifies the uncertainty in the measurement of the tSZ amplitude for the CMB S4 specification.…”