Reconstructing the radial velocity profile of cosmic voids with kinematic Sunyaev-Zeldovich Effect

Abstract

We develop an estimator to extract the mean radial velocity profile of cosmic voids via the kinematic Sunyaev-Zeldovich effect of pairs of galaxies surrounding them. The estimator is tested with simulated pure kSZ map and void catalogue data from the same simulation. The results show that the recovered signal could be attenuated by low angular resolution of the map or large aperture photometry filter radius size, but the mean radial velocity profile can be fully recovered with our estimator. By applying the estimator to the Planck 2D-ILC CMB map, with galaxy and void catalogues from BOSS DR12, we find that the estimated void velocity profile is $3.31\sigma$ apart from null detection for for voids with continuously rising density profiles asymptoting to the mean density; and $1.75\sigma$ for voids with positive density contrast shell surrounded. By fitting the reconstructed data to the theoretical profile, we find the reduced $\chi^{2}$ to be $1.19$ and $0.62$ for the two types of void, respectively, indicating a good fit of the model to the data. We then forecast the detectability of the radial velocity profile of cosmic voids with future CMB surveys, including SPT-3G, AdvACT, and Simons Observatory. We find that the contamination effect from CMB residuals is negligible with survey area over $2,000~{\rm deg}^2$, especially with aperture photometry size less than $1\,{\rm arcmin}$. But the effect from instrumental noise is non-negligible. For future SPT-3G, AdvACT and Simons Observatory, the detection is potentially achievable from $3\sigma$ to $10\sigma$ C.L., depending on specific instrumental parameters. This opens a new window of probing dynamics of the cosmic structures from the kinematic Sunyaev-Zeldovich effect.