Constraint on the massive-star growth-law parameters α and τ₀ (see Equation (2)) from the full 5D joint fit of the OB-star and embedded-source LFs. The colored map shows the profiled Δχ²(α, τ₀), obtained after minimizing over the three IMF parameters at each point in the (α, τ₀) plane. Contours correspond to the joint 1σ, 2σ, and 3σ confidence regions for the two parameters, with Δχ² = 2.30, 6.17, and 11.8. The red star marks the posterior median. The values shown in the upper-left corner give the corresponding 68% credible intervals, ﹩\alpha =0.4{8}_{-0.11}^{+0.11}﹩ and ﹩{\tau }_{0}=4.1{5}_{-0.63}^{+0.90}\,{\rm{Myr}}﹩.