2018/04/19 by Ahmad Ali, Ahmad A. Ali, Tim J. Harries +1
Physics and Astronomy · #Astrophysics #Astrophysics and Star Formation Studies #Galaxies: Formation, Evolution, Phenomena #Ion #Ionization #Monte Carlo method #Optics #Photoionization #Photon #Physics #Radiation pressure #Radiative transfer #Stellar, planetary, and galactic studies #astro-ph.GA #astro-ph.SR
paper · pdf · doi:10.1093/mnras/sty1001
16 pages, 17 figures, accepted for publication in MNRAS
arxiv created 2018/04/19 · openalex publication_date 2018/04/19 · arxiv updated 2018/04/23 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
We simulate a self-gravitating, turbulent cloud of 1000 M⊙ with photoionization and radiation pressure feedback from a 34 M⊙ star. We use a detailed Monte Carlo radiative transfer scheme alongside the hydrodynamics to compute photoionization and thermal equilibrium with dust grains and multiple atomic species. Using these gas temperatures, dust temperatures, and ionization fractions, we produce self-consistent synthetic observations of line and continuum emission. We find that all material is dispersed from the (15.5 pc)3 grid within 1.6 Myr or 0.74 free-fall times. Mass exits with a peak flux of 2 × 10−3 M⊙ yr−1, showing efficient gas dispersal. The model without radiation pressure has a slight delay in the breakthrough of ionization, but overall its effects are negligible. 85 per cent of the volume, and 40 per cent of the mass, become ionized – dense filaments resist ionization and are swept up into spherical cores with pillars that point radially away from the ionizing star. We use free–free emission at 20 cm to estimate the production rate of ionizing photons. This is almost always underestimated: by a factor of a few at early stages, then by orders of magnitude as mass leaves the volume. We also test the ratio of dust continuum surface brightnesses at 450 and 850 µm to probe dust temperatures. This underestimates the actual temperature by more than a factor of 2 in areas of low column density or high line-of-sight temperature dispersion; the |\rm H \small II| region cavity is particularly prone to this discrepancy. However, the probe is accurate in dense locations such as filaments.