Dark Matter Found From 12 Billion Years Ago
You know that mysterious substance that makes up around 85% of the total mass of the whole freakin’ universe? Yes, dark matter. We just detected some of that stuff and it’s 12 billion years old. How cool is that?
We report the first detection of the dark matter distribution around Lyman break galaxies (LBGs) at high redshift through the cosmic microwave background (CMB) lensing measurements with the public Planck PR3 κ map. The LBG sample consists of 1 473 106 objects with the median redshift of z∼4 that are identified in a total area of 305 deg2 observed by the Hyper Suprime-Cam Strategic Survey Program survey. After careful investigations of systematic uncertainties, such as contamination from foreground galaxies and cosmic infrared background, we obtain the significant detection of the CMB lensing signal at 5.1σ that is dominated by 2-halo term signals of the LBGs.
Fitting a simple model consisting of the Navarro-Frenk-White profile and the linear-bias model, we obtain the typical halo mass of Mh=2.9+9.5−2.5×1011 h−1 M⊙. Combining the CMB lensing and galaxy-galaxy clustering signals on the large scales, we demonstrate the first cosmological analysis at z∼4 that constrains (Ωm0,σ8). We find that our constraint on σ8 is roughly consistent with the Planck cosmology, while this σ8 constraint is lower than the Planck cosmology over the 1σ level.
This study opens up a new window for constraining cosmological parameters at high redshift by the combination of CMB and high-z galaxies, as well as studying the interplay between galaxy evolution and large-scale structure at such high redshift, by upcoming CMB and optical and near-infrared imaging surveys.
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