Distribution of the ammonia abundances in units of 10^-11 overlaid on an image of Spitzer/MIPS at 24 μm to highlight the second infrared ring. See details of the computation of H₂ column densities in the text. Considerable differences between the IRDC and the rest of the field are again noted; furthermore, high values appear in the northern and south edges of the SW region, coinciding with the position of the first and second infrared rings, respectively (see text).