On the peculiar momentum of baryons after Reionization

Abstract

The peculiar motion of ionized baryons is known to introduce temperature anisotropies in the CMB by means of the kinetic Sunyaev-Zel'dovich effect (kSZ). In this work, we present an all sky computation of angular power spectrum of the temperature anisotropies introduced by kSZ momentum of all baryons in the Universe during and after reionization. In an attempt to study the bulk flows of the missing baryons not yet detected, we address separately the contribution from all baryons in the IGM and those baryons located in collapsed structures like groups and clusters of galaxies. In the first case, our approach provides a complete, all sky computation of the kSZ in second order of cosmological perturbation theory (also known as the Ostriker-Vishniac effect, OV). Most of the power of OV is generated during reionization, although it has a non-negligible tail at low redshifts, when the bulk of the kSZ peculiar momentum of the halo (cluster + group) population arises. If gas outside halos is comoving with clusters as the theory predicts, then the signature of the bulk flows of the missing baryons should be recovered by a cross-correlation analysis of future CMB data sets with kSZ estimates in clusters of galaxies. For an ACT or SPT type of CMB experiment, all sky kSZ estimates of all clusters above $2\times 10^{14}{h}^{-1}{M}_{\odot }$ should provide a detection of {\it dark} flows with signal to noise ratio (S/N) of $\sim 10$, (S/N $\sim 2.5-5$ for 2,000 - 10,000 square degrees). Improving kSZ estimates with data from Large Scale Structure surveys should enable a deeper confrontation of the theoretical predictions for bulk flows with observations. The combination of future CMB and optical data should shed light on the dark flows of the nearby, so far undetected, diffuse baryons.

18 pages, 4 pages, submitted to MNRAS, incorporating referee's comments

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• The Tau of Galaxy Clusters
• Planck intermediate results. XIII. Constraints on peculiar velocities
• Planck intermediate results. XXXVII. Evidence of unbound gas from the kinetic Sunyaev-Zeldovich effect
• The kinetic SZ tomography with spectroscopic redshift surveys
• The dark flow induced small scale kinetic Sunyaev Zel'dovich effect
• A direct measure of free electron gas via the Kinematic Sunyaev-Zel'dovich effect in Fourier-space analysis
• Ultra-light axions and the kinetic Sunyaev-Zel'dovich Effect
• Density Weighted Angular Redshift Fluctuations: a New Cosmological Observable
• The kinetic Sunyaev-Zel'dovich tomography II: probing the circumgalactic medium
• E and B modes of the CMB y-type distortions: polarised kinetic Sunyaev-Zeldovich effect from the reionisation and post-reionisation eras