ner_tags: B-Citation I-Citation I-Citation I-Citation 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 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 O O O O O O O O O O B-Citation I-Citation I-Citation O B-Citation I-Citation I-Citation I-Citation O O O O O O O O O B-Model I-Model I-Model O O O O O O O O O O O O O B-Citation I-Citation I-Citation I-Citation I-Citation O O O O O O O O O O O O O O O O O B-Software 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-Model I-Model O B-Formula I-Formula I-Formula B-Citation I-Citation I-Citation I-Citation 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 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 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 O O O O O O O O O O O O O O O B-Citation I-Citation I-Citation I-Citation I-Citation I-Citation O O O O O B-Citation I-Citation I-Citation I-Citation I-Citation 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-Citation I-Citation I-Citation I-Citation 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-Citation I-Citation I-Citation I-Citation 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-Software O O O O O O O O O O O
tokens: (Shu, Adams Susana 1987 ) do not also play a role in bringing ε SF down. We note, however, that if clouds form stars preferentially in one short burst with ε SF ≈ ε min , this presents a challenge to the survivability of these star clusters because star clusters with ε SF ≲ 10 per cent tend to dissolve after the natal gas has been removed (Baumgardt Kroupa 2007 ; Shukirgaliyev et al. 2017 ). We speculate that studies of star clusters with N -body simulations that include a centrally peaked star formation profile as in the model by Parmentier Pfalzner ( 2013 ) together with slow gas removal with velocities of approximately 10 km s −1 as predicted by our warpfield2 simulations will result in a higher survival rate even for low star formation efficiencies. 4.3.1 Giant clumps Giant clumps at redshift ∼ 1−3 with gas masses of have typical surface densities of pc −2 and are consistent with isothermal spheres, i.e. α = −2 (Ceverino et al. 2012 ). In this paper we probe the lower mass end of such clumps. Our results indicate that they are more resilient against destruction by stellar feedback than clouds with shallower density profiles. As noted above, this is due to the larger binding energy of the giant clump and in particular of the inner region when α = −2 (see equation 28 ). As more of the gas mass is accumulated in the inner regions, an expanding shell in a cloud with such a steep density profile decelerates faster, making it more susceptible to energy loss via leakage of hot gas after gravitational fragmentation and via strong cooling. Our results indicate that giant clumps at the low-mass end () can be destroyed by a single starburst with ε SF ≥ 4 per cent for pc −2 ( per cent for pc −2 ). Were the star formation spread out over the lifetime of the clump (∼30 Myr), this would correspond to ε ff = 0.5 per cent ( per cent for pc −2 ). This result is in line with simulations by Oklopčić et al. ( 2017 ) but puts analytic models by Krumholz Dekel ( 2010 ) into question who argue that star formation efficiencies per free-fall time of a few per cent are insufficient to disrupt a giant molecular clump (they focus on clumps with though). Our result does not yet take into account that the metallicity in galaxies at ∼ 2 is approximately a factor 2 lower than in present-day galaxies (Yuan, Kewley Richard 2012 ), which will affect the amount of radiative cooling, the strength of metal-line-driven winds of massive stars, and the coupling of radiation to the ISM. We plan to revisit giant clumps with warpfield in the future. 5 CONCLUSION In this paper we have presented improvements to the 1D stellar feedback code warpfield (Rahner et al. 2017 ). warpfield is a fast, publicly available code which models the formation of a shell around a massive cluster and how this shell is affected by stellar winds, radiation, and SNe, as well as gravity. The improvements which are part of a new code release, warpfield2 , include, but are not limited to, a better treatment of