Constraints on Local Primordial Non-Gaussianity with 3D Velocity Reconstruction from the Kinetic Sunyaev-Zeldovich...

Area of Science:

• Cosmology
• Astrophysics
• Large-scale structure

Background:

• The cosmic velocity field traces the total matter distribution but is difficult to measure directly at high redshifts.
• The kinetic Sunyaev-Zeldovich (kSZ) effect imprints the large-scale velocity field onto the cosmic microwave background (CMB).

Purpose of the Study:

• To perform the first 3D reconstruction of the large-scale velocity field using the kSZ effect.
• To constrain cosmological parameters, specifically primordial non-Gaussianity (f_NL).

Main Methods:

• Applied a quadratic estimator to CMB temperature maps and 3D galaxy positions.
• Combined Atacama Cosmology Telescope (ACT) and Planck CMB data with Sloan Digital Sky Survey (SDSS) galaxy data.
• Measured the galaxy-velocity cross-power spectrum to detect the kSZ signal.

Main Results:

• Successfully detected the kSZ signal in the galaxy-velocity cross-correlation with a signal-to-noise ratio of 7.2σ.
• Constrained the amplitude of local primordial non-Gaussianity to f_NL = -90_{-350}^{+210} using this cross-correlation alone.

Conclusions:

• This pathfinder measurement demonstrates the potential of combining galaxy and CMB kSZ data.
• Future joint analyses can significantly improve constraints on f_NL by mitigating sample variance.