Notes. Column 2 is the observed CO line temperature, Col. 3 the radially varying ^12/13CO abundance ratio, Col. 4 is the CO excitation temperature, and Cols. 5 and 6 are the deduced CO and ¹³CO column densities, all following Sect. 3.2 of Yuan et al. (2016). Column 7 is our fiducial excitation temperature for the optically thin or close to thin species (see Sect. 4.1). Columns 8-13 are the column densities derived using the excitation temperatures from Sect. 4.1 and Yuan et al. (2016), see footnotes below. Column 14 is the estimated filling factor from Sect. 4.3. The H₂ column densities in the last two columns are derived as in the first paragraph of Sect. 4.5, where Col. 16 is the H₂ column deduced from the ¹³CO line assuming an excitation temperature as in ^(b) below.^(a) Assumes all excitation temperatures are those derived for CO (Col. 4).^(b) Our fiducial case which attempts to account for subthermal excitation temperatures such that T_ex = T_bg + 0.5 × (T_ex,CO – T_bg).^(c) Follows Yuan et al. (2016) hypothesis where HCN and HCO⁺ excitation temperatures are equal to 2hB/k.