Simulated reconstruction of the remote dipole field using the kinetic Sunyaev Zel’dovich effect

Abstract

The kinetic Sunyaev Zel'dovich (kSZ) effect, cosmic microwave background (CMB) anisotropies induced by scattering from free electrons in bulk motion, is a primary target of future CMB experiments. In addition to shedding light on the distribution of baryons and the details of the epoch of reionization, measurements of the kSZ effect have the potential to address fundamental questions about the structure and evolution of our Universe on the largest scales and at the earliest times. This potential is unlocked by combining measurements of small-scale CMB anisotropies with large-scale structure surveys, a technique known as kSZ tomography. Previous work established a quadratic estimator for the remote dipole field, the CMB dipole observed at different locations in the Universe, given a CMB map and a redshift-binned map of large scale structure. This previous work did not include gravitational lensing, redshift space distortions, or non-linear evolution of structure. In this paper, we investigate how well the remote dipole field can be reconstructed in the presence of such effects by using mock data from a suite of simulations of gigaparsec-sized regions of the Universe. To properly model both large and small scales, we develop a novel box-in-box simulation pipeline, where small-scale information is obtained from L-PICOLA N-body simulations, and large-scale information obtained by evolving fields using linear theory and adding the resulting corrections to the N-body particle data. This pipeline allows us to create properly correlated maps of the primary CMB including lensing as well as the kSZ effect and density maps on the past light cone of an observer. Analyzing an ensemble of mocks, we find that the dipole field can be reconstructed with high fidelity over a range of angular scales and redshift bins. However, we present evidence for a bias due to the non-linear evolution of structure. We also analyze correlations with the primary CMB, investigating the ability of kSZ tomography to reconstruct the intrinsic CMB dipole. Our results constitute a proof-of-principle that kSZ tomography is a promising technique for future datasets. * jcayuso@perimeterinstitute.ca † mjohnson@perimeterinstitute.ca ‡ mertens@yorku.ca arXiv:1806.01290v1 [astro-ph.CO] 4 Jun 2018 small angular scales. Although the amplitude of fluctuations is small, of order a microkelvin, the kSZ effect has now been detected at greater than 4σ [2][3][4][5], with future experiments [6] forecasted to achieve signal to noise in excess of 10 2 .The kSZ effect can be expressed as the line of sight integral [7] ∆T T kSZ (n e ) = −σ T χre 0 dχ e a e (χ e )n e (χ e )(1 + δ e (n e , χ e ))v eff (n e , χ e ),where σ T is the Thompson cross-section,n e (χ e ) is the average electron number density at comoving distance χ e , δ e (n e , χ e ) is the electron overdensity field,n e is the angular direction on the sky to the electron, v eff (n e , χ e ) is the projection of the remote CMB dipole field (the CMB dipole observed by each electron along the line of sight), and a...

Velocity reconstruction with the cosmic microwave background and galaxy surveys

“…In this section we assess the performance of velocity reconstruction with future datasets using a suite of simulations and a reconstruction pipeline based on the quadratic estimators described in previous sections. Previous work has demonstrated the effectiveness of the quadratic estimator for reconstruction of the radial velocity field using N-body simulations both on the light cone [45] and in the box geometry [43]. There has been no previous work demonstrating the feasibility of transverse velocity potential reconstruction with the moving lens effect, a gap which we fill with the present work.…”

“…Aside from this bias, both Refs. [43] and [45] demonstrated that velocity reconstruction essentially works as advertised even for non-linear N-body simulations. An important future analysis will be to directly compare the importance of the various systematic effects discussed in this paper between Gaussian and non-linear N-body simulated datasets.…”

“…Another nonlinear effect included in Ref. [45] is redshift space distortions, which were found to have minimal impact on the reconstruction at the resolutions simulated. All previous work has relied on dark matter-only N-body simulations, making the approximation that baryons follow the N-body particles.…”

Accurate relativistic observables from post-processing light cone catalogues

“…This scheme is based on Eq. ( 31), but does not require radial binning or extracting the gravitational potential, and has been employed in a number of contexts in the literature [78][79][80][81][82],…”

Reconstruction with velocities

“…By combining future optical surveys (such as DESI DESI Collaboration et al 2016, Euclid Amendola et al 2018and LSST LSST Science Collaboration et al 2009) and Cosmic Microwave Background (CMB) experiments (such as the future Simons Observatory Ade et al 2019 andCMB-S4 Abazajian et al 2016) the radial peculiar velocities can be measured with high precision from the kSZ effect imprinted on the CMB for millions of galaxies and can be used to constrain cosmological parameters (e.g. Smith et al 2018;Münchmeyer et al 2018;Deutsch et al 2018;Cayuso et al 2018;McCarthy & Johnson 2019;Pan & Johnson 2019).…”