Abstract
Determining the large-scale distribution of baryons in the late universe is a
long-standing challenge in cosmology. To gain insight into this problem, we
present a new approach for extracting the kinematic Sunyaev-Zel'dovich (kSZ)
effect from observations, ARF-kSZ tomography. This technique involves the
cross-correlation of maps of Angular Redshift Fluctuations (ARF), which contain
precise information about the cosmic density and velocity fields, and cosmic
microwave background (CMB) temperature maps high-pass filtered using aperture
photometry. To produce the first and second, in this work we resort to galaxies
and quasars from 6dF and SDSS and foreground-cleaned CMB maps from Planck,
respectively. We detect statistically significant cross-correlation between ARF
and filtered CMB maps for a wide range of redshifts and filter apertures,
yielding a joint detection of the kSZ effect at the $>10\sigma$ level. Using
measurements of the kSZ optical depth extracted from these cross-correlations,
we then set constraints on the properties of the gas responsible for the kSZ
effect, finding that the kSZ gas resides mostly outside haloes and presents
densities from 10 to 250 times the cosmic average, which is the density of
baryons in filaments and sheets according to cosmological hydrodynamical
simulations. Finally, we conduct a tomographic census of baryons from redshift
z=0 to 5, finding that ARF-kSZ tomography is sensitive to approximately half of
the baryons in the Universe.
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