Kakiichi, K;
Gronke, M;
(2021)
Radiation Hydrodynamics of Turbulent H ii Regions in Molecular Clouds: A Physical Origin of LyC Leakage and the Associated Lyα Spectra.
The Astrophysical Journal
, 908
(1)
, Article 30. 10.3847/1538-4357/abc2d9.
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Abstract
We examine Lyman continuum (LyC) leakage through H ii regions regulated by turbulence and radiative feedback in a giant molecular cloud in the context of fully coupled radiation hydrodynamics (RHD). The physical relations of the LyC escape with H i covering fraction, kinematics, ionizing photon production efficiency, and emergent Lyα line profiles are studied using a series of RHD turbulence simulations performed with ramses-rt. The turbulence-regulated mechanism allows ionizing photons to leak out at early times before the onset of supernova feedback. The LyC photons escape through turbulence-generated low column density channels that are evacuated efficiently by radiative feedback via photoheating-induced shocks across the D-type ionization fronts. The Lyα photons funnel through the photoionized channels along the paths of LyC escape, resulting in a diverse Lyα spectral morphology including narrow double-peaked profiles. The Lyα peak separation is controlled by the residual H i column density of the channels, and the line asymmetry correlates with the porosity and multiphase structure of the H ii region. This mechanism through the turbulent H ii regions can naturally reproduce the observed Lyα spectral characteristics of some of the LyC-leaking galaxies. This RHD turbulence origin provides an appealing hypothesis to explain high LyC leakage from very young (∼3 Myr) star-forming galaxies found in the local universe without need of extreme galactic outflows or supernova feedback. We discuss the implications of the turbulent H ii regions on other nebular emission lines and a possible observational test with the Magellanic System and local blue compact dwarf galaxies as analogs of reionization-era systems.
| Type: | Article |
|---|---|
| Title: | Radiation Hydrodynamics of Turbulent H ii Regions in Molecular Clouds: A Physical Origin of LyC Leakage and the Associated Lyα Spectra |
| Open access status: | An open access version is available from UCL Discovery |
| DOI: | 10.3847/1538-4357/abc2d9 |
| Publisher version: | http://dx.doi.org/10.3847/1538-4357/abc2d9 |
| Language: | English |
| Additional information: | This version is the version of record. For information on re-use, please refer to the publisher’s terms and conditions. |
| UCL classification: | UCL UCL > Provost and Vice Provost Offices > UCL BEAMS UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences |
| URI: | https://discovery-pp.ucl.ac.uk/id/eprint/10138940 |
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