Map of the abundance ratio /. The contours show the value of / = 4. The letters A to I present the selected regions where the abundance ratio is lower (A, B, C, E, F, and G) and much higher (region D), and the outskirts (H and I). The black circle presents the location of the W 40 H II region (radius ∽ 3′) and the black filled circle in the bottom-right illustrates the beam size of 60′′. The clippinglevel for the ¹³CO and C¹⁸O data is the S/N greater than five. High abundance-ratio values are distributed only in region D and reach up to 42.