χ² landscape of the initial broad search for the injection index α_inj. Left: Northern lobe. Right: Southern lobe. Squares indicate the explored values. Dotted lines are cubic spline fits for illustrative purposes. The large panels show the χ² values for the broad search from 0.5 to 1.0. The insets show the χ² values for the detailed search in a narrower range of 0.75−0.85 (left) and 0.55−0.65 (right).