is the solid angle of the subtended by the source.

The H$_2$ mass of the clouds can be calculated from the observed CO(1-0) luminosity assuming a linear conversion between the velocity integrated CO emission ($I_{\textrm{CO}}$) and the H$_2$ column density ($N_{{\rm H}_2}$); $$N_{\rm H{_2}} = X_{\textrm{CO}}\, [cm^{-2}(K{\rm kms^{-1}})^{-1}]\,\, I_{\textrm{CO}}\,[K{\rm kms^{-1}}],$$ where $X_{\textrm{CO}}$ is the CO-to-H$_2$ conversion factor (Bolatto et al. 2013; Roman-Duval et al. 2014). The total mass of H$_2$ ($M_{{\rm H}_2}$) is, $$M_{\textrm{H}_2} \,[M_\odot] = \alpha_{\textrm{CO}} {\rm D}^2\, [{\rm Mpc}] S_{\textrm{CO}},$$ where $$\alpha_{\textrm{CO}}\, [M_\odot {\rm Mpc}^{-2} ({\it Jy}{\rm kms}^{-1})^{-1}] = X_{\textrm{CO}} \frac{m_{\textrm{H}_2} c^2}{2 k \nu^2},$$ and the flux density $S_{\textrm{CO}}$ is, $$S_{\textrm{CO}}\,\, [{\it Jy}{\rm kms}^{-1}] = \int S_{\nu} \, dv.$$ The molecular gas mass is multiplied by 1.36 to include the Helium contribution. This method is calibrated for the $J$=1$\rightarrow$0 transition. We use a ratio between the CO$J$=2$\rightarrow$1 and $J$=1$\rightarrow$0 lines of 0.87 for 30 Doradus Cloud 10 (the North Eastern cloud; see Fig.1) found by Johannson et al. (1998) to estimate the CO(1-0) luminosity.

The conversion factor depends on both metallicity and the ambient radiation field intensity (Maloney 1988). As a consequence of strong radiation fields and poor self-shielding in low metallicity environments, the CO molecule is photo-dissociated 