2021/02/28 by Aleksandra Kusiak, Boris Bolliet, Simone Ferraro +2
Physics and Astronomy · #Anisotropy #Astrophysics #CMB cold spot #Cosmic microwave background #Cosmology and Gravitation Theories #Galaxies: Formation, Evolution, Phenomena #Galaxy #Physics #Planck #Quantum mechanics #Radio Astronomy Observations and Technology #Redshift #Sunyaev–Zel'dovich effect #astro-ph.CO
paper · pdf · doi:10.1103/physrevd.104.043518
published as Phys. Rev. D 104, 043518 (2021) · Matches the version accepted for publication in PRD (https://journals.aps.org/prd/accepted/d907bQ13Oae1fd21e4ff4f13177300acb1c23e88e)
openalex created_date 2021/02/15 · arxiv created 2021/07/16 · openalex publication_date 2021/08/16 · arxiv updated 2021/08/25 · openalex updated_date 2026/08/05
The kinematic Sunyaev-Zel'dovich (kSZ) effect---the Doppler boosting of Cosmic Microwave Background (CMB) photons scattering off free electrons with nonzero line-of-sight velocity---is an excellent probe of the distribution of baryons in the Universe. In this paper, we measure the kSZ effect due to ionized gas traced by infrared-selected galaxies from the unWISE catalog. We employ the ``projected-field'' kSZ estimator, which does not require spectroscopic galaxy redshifts. To suppress contributions from non-kSZ signals associated with the galaxies (e.g., dust emission and thermal SZ), this estimator requires foreground-cleaned CMB maps, which we obtain from Planck and WMAP data. Using a new ``asymmetric'' estimator that combines different foreground-cleaned CMB maps to maximize the signal-to-noise, we measure the kSZ2-galaxy cross-power spectrum for three subsamples of the unWISE galaxy catalog. These subsamples peak at mean redshifts z\ensuremath≈0.6, 1.1, and 1.5, have average halo mass \ensuremath∼1--5\ifmmode×\else\texttimes\fi1013 h^\ensuremath-1M_\ensuremath\bigodot, and in total contain over 500 million galaxies. After marginalizing over contributions from CMB lensing, we measure the amplitude of the kSZ signal A_kSZ2=0.42\ifmmode±\else\textpm\fi0.31(stat)\ifmmode±\else\textpm\fi0.02(sys), 5.02\ifmmode±\else\textpm\fi1.01(stat)\ifmmode±\else\textpm\fi0.49(sys), and 8.23\ifmmode±\else\textpm\fi3.23(stat)\ifmmode±\else\textpm\fi0.57(sys), for the three subsamples, where A_kSZ2=1 corresponds to our fiducial theoretical model. The combined statistical significance of our kSZ detection exceeds 5\ensuremathσ. Our theoretical model includes the first calculation of lensing magnification contributions to the kSZ2-galaxy cross-power spectrum, which are significant for the z\ensuremath≈1.1 and 1.5 subsamples. We discuss possible explanations for the excess kSZ signal associated with the z\ensuremath≈1.1 sample, and show that foreground contamination in the CMB maps is very unlikely to be the cause. From our measurements of A_kSZ2, we constrain the product of the baryon fraction fb and free electron fraction ffree to be (fb/0.158)(ffree/1.0)=0.65\ifmmode±\else\textpm\fi0.24, 2.24\ifmmode±\else\textpm\fi0.25, and 2.87\ifmmode±\else\textpm\fi0.57 at z\ensuremath≈0.6, 1.1, and 1.5, respectively, consistent with a large fraction of the cosmic baryon abundance existing in an ionized state at low redshifts.