The kinetic Sunyaev-Zeldovich (kSZ) effect has now become a clear target for
ongoing and future studies of the cosmic microwave background (CMB) and
cosmology. Aside from the bulk cluster motion, internal motions also lead to a
kSZ signal. In this work, we study the rotational kSZ effect caused by coherent
large-scale motions of the cluster medium using cluster hydrodynamic
cosmological simulations. To utilise the rotational kSZ as a cosmological
probe, simulations offer some of the most comprehensive data sets that can
inform the modeling of this signal. In this work, we use the MACSIS data set to
specifically investigate the rotational kSZ effect in massive clusters. Based
on these models, we test stacking approaches and estimate the amplitude of the
combined signal with varying mass, dynamical state, redshift and map-alignment
geometry. We find that the dark matter, galaxy and gas spins are generally
misaligned, an effect that can cause a sub-optimal estimation of the rotational
kSZ effect when based on galaxy catalogues. Furthermore, we provide
halo-spin-mass scaling relations that can be used to build a statistical model
of the rotational kSZ. The rotational kSZ contribution, which is largest in
massive unrelaxed clusters (≳100 μK), could be relevant to studies
of higher-order CMB temperature signals, such as the moving lens effect. The
limited mass range of the MACSIS sample strongly motivates an extended
investigation of the rotational kSZ effect in large-volume simulations to
refine the modelling, particularly towards lower mass and higher redshift, and
provide forecasts for upcoming cosmological CMB experiments (e.g. Simons
Observatory, SKA-2) and X-ray observations (e.g. \textit{Athena}/X-IFU).Comment: Submitted to Monthly Notices of the Royal Astronomical Society.
Comments and discussions are welcome. Data and codes can be found at
https://github.com/edoaltamura/macsis-cosmosi