Modeling UV Radiation Feedback from Massive Stars: III. Escape of Radiation from Star-forming Giant Molecular Clouds

Abstract

Using a suite of radiation hydrodynamic simulations of star cluster formation in turbulent clouds, we study the escape fraction of ionizing (Lyman continuum) and non-ionizing (FUV) radiation for a wide range of cloud masses and sizes. The escape fraction increases as H II regions evolve and reaches unity within a few dynamical times. The cumulative escape fraction before the onset of the first supernova explosion is in the range 0.05-0.58; this is lower for higher initial cloud surface density, and higher for less massive and more compact clouds due to rapid destruction. Once H II regions break out of their local environment, both ionizing and non-ionizing photons escape from clouds through fully ionized, low-density sightlines. Consequently, dust becomes the dominant absorber of ionizing radiation at late times and the escape fraction of non-ionizing radiation is only slightly larger than that of ionizing radiation. The escape fraction is determined primarily by the mean $⟨\tau ⟩$ and width $\sigma$ of the optical-depth distribution in the large-scale cloud, increasing for smaller $⟨\tau ⟩$ and/or larger $\sigma$. The escape fraction exceeds (sometimes by three orders of magnitude) the naive estimate $e^{-⟨\tau ⟩}$ due to non-zero $\sigma$ induced by turbulence. We present two simple methods to estimate, within $\sim 20\%$, the escape fraction of non-ionizing radiation using the observed dust optical depth in clouds projected on the plane of sky. We discuss implications of our results for observations, including inference of star formation rates in individual molecular clouds, and accounting for diffuse ionized gas on galactic scales.

27 pages, 16 figures, accepted for publication in ApJ

References in corpus (25)

• Theory of Star Formation
• Athena: A New Code for Astrophysical MHD
• Cosmic Reionization and Early Star-Forming Galaxies: A Joint Analysis of New Constraints from Planck and Hubble Space Telescope
• Escape fraction of ionizing photons during reionization: effects due to supernova feedback and runaway OB stars
• Conditions for Reionizing the Universe with A Low Galaxy Ionizing Photon Escape Fraction
• The First Billion Years Project: The escape fraction of ionizing photons in the epoch of reionization
• Herschel-Planck dust optical-depth and column-density maps: I. Method description and results for Orion
• A Local Clue to the Reionization of the Universe
• Feedback-regulated star formation and escape of LyC photons from mini-haloes during reionisation
• Superbubbles in the Multiphase ISM and the Loading of Galactic Winds
• Q1549-C25: A Clean Source of Lyman-Continuum Emission at $z=3.15$
• Diffuse ionized gas in galaxies across the Hubble sequence at the CALIFA resolution
• Magnetohydronamic Evolution of HII Regions in Molecular Clouds: Simulation Methodology, Tests, and Uniform Media
• Mutual influence of supernovae and molecular clouds
• A Detailed Study of Feedback from a Massive Star
• Galaxies that Shine: radiation-hydrodynamical simulations of disk galaxies
• Understanding the escape of LyC and Ly$\alpha$ photons from turbulent clouds
• Numerical Simulations of Turbulent, Molecular Clouds Regulated by Radiation Feedback Forces I: Star Formation Rate and Efficiency
• A Census of the Carina Nebula -- II. Energy Budget and Global Properties of the Nebulosity
• The Polycyclic Aromatic Hydrocarbon Mass Fraction on a 10 pc scale in the Magellanic Clouds
• The Effects of Diffuse Ionized Gas and Spatial Resolution on Metallicity Gradients: TYPHOON Two-Dimensional Spectrophotometry of M83
• Modeling UV Radiation Feedback from Massive Stars: I. Implementation of Adaptive Ray Tracing Method and Tests
• The Orion HII Region and the Orion Bar in the Mid-Infrared
• Numerical Simulations of Turbulent Molecular Clouds Regulated by Radiation Feedback Forces II: Radiation-Gas Interactions and Outflows
• Ultra Violet Escape Fractions from Giant Molecular Clouds During Early Cluster Formation

Cited by in corpus (36)

• No missing photons for reionization: moderate ionizing photon escape fractions from the FIRE-2 simulations
• Star Formation Efficiency and Dispersal of Giant Molecular Clouds with UV Radiation Feedback: Dependence on Gravitational Boundedness and Magnetic Fields
• Pressure-Regulated, Feedback-Modulated Star Formation In Disk Galaxies
• Efficiently Cooled Stellar Wind Bubbles in Turbulent Clouds I. Fractal Theory and Application to Star-Forming Clouds
• Efficient early stellar feedback can suppress galactic outflows by reducing supernova clustering
• Efficiently Cooled Stellar Wind Bubbles in Turbulent Clouds II. Validation of Theory with Hydrodynamic Simulations
• The contribution from stars stripped in binaries to cosmic reionization of hydrogen and helium
• Nitrogen-enriched, highly-pressurized nebular clouds surrounding a super star cluster at cosmic noon
• Star cluster formation and cloud dispersal by radiative feedback: dependence on metallicity and compactness
• Simulating the interstellar medium of galaxies with radiative transfer, non-equilibrium thermochemistry, and dust
• Comparing the pre-SNe feedback and environmental pressures for 6000 HII regions across 19 nearby spiral galaxies
• Star Formation Regulation and Self-Pollution by Stellar Wind Feedback
• Momentum feedback from marginally-resolved HII regions in isolated disc galaxies
• Testing the role of environmental effects on the initial mass function of low-mass stars
• A systematic study of the escape of LyC and Ly$\alpha$ photons from star-forming, magnetized turbulent clouds
• Outflows from Super Star Clusters in the Central Starburst of NGC253
• Diffuse Ionized Gas in Simulations of Multiphase, Star-Forming Galactic Disks
• The connection between galactic outflows and the escape of ionizing photons
• Inferring the HII region escape fraction of ionizing photons from infrared emission lines in metal-poor star-forming dwarf galaxies
• Effects of initial density profiles on massive star cluster formation in giant molecular clouds
• Two Modes of LyC Escape From Bursty Star Formation: Implications for [C II] Deficits and the Sources of Reionization
• Photoionising feedback in spiral arm molecular clouds
• On the origin of low escape fractions of ionizing radiation from massive star-forming galaxies at high redshift
• The IACOB project X. Large-scale quantitative spectroscopic analysis of Galactic luminous blue stars
• The SATIN project I: Turbulent multi-phase ISM in Milky Way simulations with SNe feedback from stellar clusters
• Detection of He++ ion in the star-forming ring of the Cartwheel using MUSE data and ionizing mechanisms
• Ionizing photon production and escape fractions during cosmic reionization in the TNG50 simulation
• Astraeus VIII: A new framework for Lyman-$\alpha$ emitters applied to different reionisation scenarios
• The effects of local stellar radiation and dust depletion on non-equilibrium interstellar chemistry
• The contribution of globular clusters to cosmic reionization
• PHANGS-ALMA: Arcsecond CO(2-1) Imaging of Nearby Star-Forming Galaxies
• Pre-supernova feedback mechanisms drive the destruction of molecular clouds in nearby star-forming disc galaxies
• Dust Grain Growth at High Redshift: Starburst-driven CMB-Dark Supershells
• Gaseous nebulae and massive stars in the giant HI ring in Leo
• Cloud fragmentation cascades and feedback: on reconciling an unfettered inertial range with a low star formation rate
• Stellar associations powering HII regions $\unicode{x2013}$ II. Escape fraction of ionizing photons