white line in the top panel. The slit cuts along the centre of the stapler nebula. [*Bottom*]{}: CO(2-1) spectra of each cloud extracted from the region bounded by the contours shown in top panel. The dashed lines for each cloud is it’s $V_{\rm{lsr}}$ given in Table 1. []{data-label="fig:spectra"}](spectra.pdf "fig:"){width="49.50000%"}

Physical properties
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After identifying each cloud, we computed the central velocity ($V_{\rm lsr}$) in the local standard of rest frame, and velocity width ($\sigma_{v}$) by fitting a Gaussian profile to the total cloud spectrum. The major and minor axis sizes of the profiles, in conjunction with the rms size of the beam were used to compute the deconvolved radius ($r$). Given the uncertainties on the Gaussian fit of the CO spectra found for each cloud are around 30%, we estimate the uncertainties on $r$ to be 15%.

### CO luminosity and mass

The CO cloud luminosity is computed as: $$L_{\rm CO}\, [K{\rm kms}^{-1}{\rm pc}^{-2}] = \rm{D}^2 \int_{\Omega} \int_v T_{\rm mb}(\nu) \, d\nu \,d\Omega$$ where D is the distance to the source in pc (adopted as 50kpc), $T_{\rm mb}$ the main beam temperature which is the antenna temperature corrected for the efficiency of the antenna ($T_{\rm mb} = T_{\textrm{A}}/\eta$), and $\Omega$ 