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We perform a suite of 3D radiation hydrodynamics simulations ofphotoevaporation of molecular gas clumps illuminated by external massive stars.We study the fate of solar-mass clumps and derive their lifetimes with varyingthe gas metallicity over a range of $10^{-3} \,Z_\odot \leq Z \leq Z_\odot $.Our simulations incorporate radiation transfer of far ultraviolet (FUV) andextreme ultraviolet (EUV) photons, and follow atomic/molecular line cooling anddust-gas collisional cooling. Nonequilibrium chemistry is coupled with theradiative transfer and hydrodynamics in a self-consistent manner. We show thatradiation-driven shocks compress gas clumps to have a volume that is set by thepressure-equilibrium with the hot ambient gas. Radiative cooling enablesmetal-rich clumps to condense and to have small surface areas, wherephotoevaporative flows are launched. For our fiducial set-up with an O-typestar at a distance of 0.1 parsec, the resulting photoevaporation rate is assmall as $\sim 10^{-5} M_{\odot}/{\rm yr}$ for metal-rich clumps, but is largerfor metal-poor clumps that have larger surface areas. The clumps arecontinuously accelerated away from the radiation source by the so-called rocketeffect, and can travel over $\sim$1 parsec within the lifetime. We also studyphotoevaporation of clumps in a photo-dissociation region. Photoelectricheating is inefficient for metal-poor clumps that contain a smaller amount ofgrains, and thus they survive for over $10^5$ years. We conclude that the gasmetallicity strongly affects the clump lifetime and thus determines thestrength of feedback from massive stars in star-forming regions.

Photoevaporation of Molecular Gas Clumps Illuminated by External Massive Stars: Clump Lifetimes and Metallicity Dependence