A Cosmic Sketch Without Smudges: JWST Confirms Cold Dark Matter ✦
Original: "The free-streaming length of dark matter from JWST observations of 28 strong gravitational lenses"
Analysis of 28 gravitational lenses with JWST set tight limits on the free-streaming length of dark matter particles, confirming its 'cold' nature and the crisp precision of the cosmic blueprint.
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To weigh the invisible, astronomers turned 28 distant quasars into cosmic microscopes. Each split arc is a cast of thousands of dark clumps. The verdict: dark matter is cold, heavy, and sketches the Universe without a tremble. Not a single smudge. But the next step is to check if the hand will waver when we crank up the magnification to full.
🎯 Astronomers used a clever trick: by observing the warm dust around quasars with MIRI, they turned it into a natural diffuser, averaging out the flickering of microlensing stars and revealing dark clumps with masses as low as a million Suns — the size of a dwarf galaxy.
m_{\mathrm{hm}} = M_0 \left(\frac{m_{\mathrm{therm}}}{3\ \mathrm{keV}}\right)^\zeta
For spin-1/2 fermions, M₀ = 4.0×10⁸ M⊙, ζ = –3.564; for spin-3/2, 2.1×10⁸ M⊙, ζ = –3.585. Shows how quickly the formation of small halos is suppressed as the particle mass decreases.
\lambda_{\mathrm{FS}} = 5.2 \left(\frac{m_{\mathrm{hm}}}{10^7 \, M_\odot}\right)^{1/3} \ \mathrm{кпк}
Approximate distance particles can travel before fluctuation growth begins at the epoch of matter-radiation equality. The lighter the particles, the larger λ_FS and the more smeared the small-scale structure.