★★☆ Moderate

🌌 Dark Matter Halo

Explore the invisible structure of galaxies. The NFW dark matter halo profile explains why rotation curves stay flat far from galactic centres — evidence for dark matter.

Halo mass M₂₀₀ (log M☉): 12.0 Concentration c: 10 Stellar fraction f★: 0.03

M₂₀₀: 10¹² M☉

rs: -

ρ₀: -

v_max: -

DM fraction at 15 kpc: -

NFW Profile & Rotation Curves

The Navarro-Frenk-White (NFW) profile describes how dark matter density varies with radius in CDM simulations: ρ(r) = ρ₀ / [(r/r_s)(1 + r/r_s)²], where r_s = r₂₀₀/c is the scale radius and c is the concentration parameter.

The enclosed mass is M(r) = 4π ρ₀ r_s³ [ln(1+r/r_s) − (r/r_s)/(1+r/r_s)], giving circular velocity v_c(r) = √(GM(r)/r).

Left panel: 2D projected density map — brighter = higher density. The stellar disk appears as the compact central bulge. Right panel: rotation curves — the green dashed line shows stars-only (Keplerian fall-off), the blue dashed line shows DM-only, and the solid white curve is the observed total.

Real galaxies show flat rotation curves well beyond the stellar disk — direct evidence that dark matter provides a dominant mass component in the outer halo.