Observed brightness profile (black) in the 3.35 μm photometric band, compared with modeled profiles (colored) for varying density parameters n₀ (from 10⁵ to 8 × 10⁵ H cm⁻³, left) with z₀ fixed to 7 × 10⁻³ pc and z₀ (from 2 × 10⁻³ to 9 × 10⁻³ pc, right) with n₀ fixed to 4 × 10⁵ H cm⁻³). The modeling was performed using the following dust properties: M_a–C/M_H, = 2.3 × 10⁻³, a_min,a–C = 0.53 nm, and α = −4. The incident radiation field, illuminating the Horsehead nebula from the right, corresponds to a blackbody at 34 600 K with G₀ = 100. All emission profiles have been convolved with the PSFs and normalized to the observed filament.