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arXiv · 1607.07166

Lyman-alpha radiation hydrodynamics of galactic winds before cosmic reionization

Aaron Smith·Volker Bromm·Abraham Loeb
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Abstract

The dynamical impact of Lyman-alpha (Lyα) radiation pressure on galaxy formation depends on the rate and duration of momentum transfer between Lyα photons and neutral hydrogen gas. Although photon trapping has the potential to multiply the effective force, ionizing radiation from stellar sources may relieve the Lyα pressure before appreciably affecting the kinematics of the host galaxy or efficiently coupling Lyα photons to the outflow. We present self-consistent Lyα radiation-hydrodynamics simulations of high-$z$ galaxy environments by coupling the Cosmic Lyα Transfer code (COLT) with spherically symmetric Lagrangian frame hydrodynamics. The accurate but computationally expensive Monte-Carlo radiative transfer calculations are feasible under the one-dimensional approximation. The initial starburst drives an expanding shell of gas from the centre and in certain cases Lyα feedback significantly enhances the shell velocity. Radiative feedback alone is capable of ejecting baryons into the intergalactic medium (IGM) for protogalaxies with a virial mass of $M_{\rm vir} \lesssim 10^8~{\rm M}_\odot$. We compare the Lyα signatures of Population III stars with $10^5$ K blackbody emission to that of direct collapse black holes with a nonthermal Compton-thick spectrum and find substantial differences if the Lyα spectra are shaped by gas pushed by Lyα radiation-driven winds. For both sources, the flux emerging from the galaxy is reprocessed by the IGM such that the observed Lyα luminosity is reduced significantly and the time-averaged velocity offset of the Lyα peak is shifted redward.

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Aaron Smith, Volker Bromm, Abraham Loeb. 2016-10-25. Lyman-alpha radiation hydrodynamics of galactic winds before cosmic reionization. https://doi.org/10.1093/mnras%2Fstw2591

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