pub fn visibility_j_bb(z: f64) -> f64Expand description
Thermalization visibility: probability that energy injection at z is fully thermalized into a blackbody (temperature shift).
J_bb(z) = exp(−(z/z_μ)^{5/2})
where z_μ ≈ 1.98×10⁶. Both z_μ and the exponent 5/2 are analytically derived: z_μ from equating the DC+BR photon production rate to the Hubble rate in radiation domination (Chluba & Sunyaev 2012), and 5/2 from the redshift scaling of the DC opacity ∝ (1+z)^{−9/2} vs H ∝ (1+z)^{−2} (Danese & de Zotti 1982; Hu & Silk 1993). These are NOT fit parameters.