Using dark matter distribution to test the cosmological model

 arXiv:

We present cosmology results from a blinded joint analysis of cosmic shear, ξ±(ϑ), galaxy-galaxy weak lensing, ΔΣ(R), and projected galaxy clustering, wp(R), measured from the Hyper Suprime-Cam three-year (HSC-Y3) shape catalog and the Sloan Digital Sky Survey (SDSS) DR11 spectroscopic galaxy catalog - a 3×2pt cosmology analysis.

We obtain a robust constraint on the cosmological parameters for the flat ΛCDM model: S8=σ8(Ωm/0.3)0.5=0.763+0.040−0.036 (68% C.I.), or the best-constrained parameter given by S′8=σ8(Ωm/0.3)0.22=0.721±0.028, determined with about 4% fractional precision.

Phys.org:

An international team of astrophysicists and cosmologists at various institutes including the Kavli Institute for the Physics and Mathematics of the Universe (Kavli IPMU) have submitted a set of five papers, measuring a value for the "clumpiness" of the universe's dark matter, known to cosmologists as S8, of 0.76, which aligns with values that other gravitational lensing surveys have found in looking at the relatively recent universe, but it does not align with the value of 0.83 derived from the cosmic microwave background, which dates back to the universe's origins when the universe was about 380,000 years old. 

Previously on this blog: 

• Discovery of an isolated dark dwarf galaxy in the nearby universe

Discovery of an isolated dark dwarf galaxy in the nearby universe

arXiv (accepted for publication in ApJ):  

Based on a new H I survey using the Five-hundred-meter Aperture Spherical radio Telescope (FAST), combined with the Pan-STARRS1 images, we identified an isolated H I cloud without any optical counterpart, named FAST J0139+4328...These findings provide observational evidence that FAST J0139+4328 is an isolated dark dwarf galaxy with a redshift of z = 0.0083.

Moreover, this disk galaxy has an extremely low absolute magnitude (M_B >-10.0 mag).

This is an insanely low absolute magnitude. For reference, a normal absolute magnitude for a galaxy like this might be around 10.

Furthermore, we obtained that the H I mass of this galaxy is (8.3±1.7)e7 SM, and the dynamical mass to total baryonic mass ratio is 47±27, implying that dark matter dominates over baryons in FAST J0139+4328. 

That's a substantial error bar--I wonder if future observations can constrain that much better.

ScienceAlert:

And they got a hit: the radio waves emitted by a cloud of HI 94 million light-years away were consistent with a rotating disk galaxy, without the optical light expected of one. Follow-up observations in infrared and ultraviolet revealed a faint smattering of stars.

 "This is the first time that a gas-rich isolated dark galaxy has been detected in the nearby Universe," the researchers write.

There are a few other dark galaxy candidates, namely HI 1225+01 (ADS) and HI1232+20 (arXiv).