Abstract
Abstract
The kinematic Sunyaev-Zel'dovich (kSZ) effect has been detected at z < 1 using various
techniques and data sets. The ongoing and upcoming spectroscopic galaxy surveys such as DESI (Dark
Energy Spectroscopic Instrument) and PFS (Prime Focus Spectrograph) will push the detection beyond
z = 1, and therefore map the baryon distribution at high redshifts. Such detection can be
achieved by both the kSZ stacking and tomography methods. While the two methods are theoretically
equivalent, they differ significantly in the probed physics and scales, and required data
sets. Taking the combination of PFS and ACT (Atacama Cosmology Telescope) as an example, we build
mocks of kSZ and galaxies, quantify the kSZ detection S/N, and compare between the two methods.
We segment the PFS galaxies into three redshift bins: 0.6 < z < 1.0, 1.0 < z < 1.6, and 1.6 <
z < 2.4. For tomography method, our analysis reveals that the two higher redshift bins exhibit
significantly higher S/N ratios, with values of 32 and 28, respectively, compared to the first
redshift bin, which yielded an S/N of 8. This is attributed to not only the increasing of electron
density with redshifts, but also the larger survey volume and the reduced non-linearity,
facilitating velocity reconstruction at higher redshifts. Therefore, the capability of the PFS
survey to measure high redshift kSZ effect stands as a substantial advantage over other
spectroscopic surveys at lower redshift. The S/N of kSZ stacking largely depends on the number of
galaxy groups available from another photometric survey. But in general, its S/N is lower than
that of kSZ tomography, largely due to CMB instrument noise and error in galaxy group redshift.
Incorporating next-generation CMB surveys like CMB-S4, characterized by significantly reduced
instrument noise and improved angular resolution, is expected to enhance tomographic detection by
a factor of ten and stacking detection by fivefold. This future high S/N detection holds the
promise of not only providing precise constraints on the overall baryon abundance but also
initiating a new insight into baryon distribution.