ner_tags: O O O O O O O O O O O O O O O B-Formula I-Formula I-Formula I-Formula I-Formula I-Formula I-Formula O O O B-Wavelength O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B-Formula I-Formula I-Formula I-Formula I-Formula I-Formula I-Formula I-Formula I-Formula I-Formula O O O O O O O O O O O O O O O O O O B-Formula I-Formula I-Formula I-Formula I-Formula I-Formula I-Formula I-Formula I-Formula I-Formula I-Formula I-Formula O O O O O O O O O O O O O O O O O O O O O O O O O B-Wavelength O O O O O O O O O O O O O O O B-Wavelength O O O O O O O O O O O O O O O O O O O O O O B-Wavelength O B-Wavelength O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B-Formula I-Formula I-Formula I-Formula I-Formula I-Formula I-Formula O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B-Wavelength O B-Wavelength O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B-Formula I-Formula I-Formula I-Formula O O O O O B-Wavelength O O O O O O O O O O O O O O O B-Wavelength O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B-Wavelength O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O
tokens: the same plots as Fig. 5(a) but for the cases with more massive clouds with M cl = 10 6 M ⊙ , where the FUV feedback effects are more remarkable than other cases. In this case, T out is much higher than the threshold temperature 100 K for any range of Σ cl . This is due to the dependence of G out ∝ S FUV Σ cl / M cl again. With a fixed value of Σ cl , G out is larger with higher M cl because G out ∝ ε S FUV / M * = εΞ FUV and ε is enhanced following equation ( 22 ). The SFE required to disrupt the natal cloud is much smaller than the case only with EUV feedback. Fig. 5(b) also suggests that even with a large threshold temperature ≲700 K, the FUV feedback should still reduce the minimum SFE ε min . 3.3 Chemical compositions of molecular cloud remnants Our calculations suggest that the EUV and FUV radiative feedback from forming clusters jointly contribute to reduce the SFE of molecular clouds. In this section, we cast light on the gas that has not been used for star formation (i.e. the ‘remnants’ of the clouds). The cloud remnants still retain a large part of the cloud materials because the obtained SFEs are much smaller than unity for many cases. We focus on the chemical compositions of the cloud remnants, which are also followed in our calculations. We calculate the masses of H i , CO-dark and CO-bright H 2 gases as follows: First, we consider the cases with the fixed cloud mass M cl = 10 5 M ⊙ . Fig. 6(a) presents the mass fraction of the gas with the different chemical properties as functions of Σ cl . The neutral and molecular hydrogen are the dominant components of the cloud remnants, and they occupy 70 and 30 per cent of the total mass, respectively. In particular, we distinguish H 2 molecules associated with CO molecules and those without CO. The H 2 gas without CO molecules is the so-called ‘CO-dark’ molecular gas. Let us look at the cases where the minimum SFE is limited by the EUV and FUV feedback (Criterion 2, solid lines). Fig. 6(a) shows that most of the H 2 molecules contained in the remnants are actually CO-dark. Such a trend only has a weak dependence on Σ cl ; the mass of the CO-dark H 2 gas is generally much less than 10 per cent of that of the H 2 gas associated with CO molecules. This is caused by the different shielding processes of H 2 and CO molecules. As shown in Fig. 6(c) , the column density of the shell is roughly , corresponding to A V ≃ 1–3.5. The dust attenuation of the FUV radiation is not very efficient for such cases. In fact, Fig. 6(b) shows that the FUV flux at the shock front non-dimensional quantity ( G out ) is several to several tens, which is high enough to photodissociate CO molecules. However, H 2 molecules are protected against the FUV radiation by the self-shielding effect even with the small column densities. As self-shielding is not available for CO molecules, which only have small abundance, CO molecules are selectively destroyed. Figure 6. Chemical compositions of the gas that has not been