Radiation Forces on Dust Envelopes

Abstract

We address in detail the radiation forces on spherical dust envelopes around luminous stars, and numerical solutions for these forces, as a first step toward more general dust geometries. Two physical quantities, a normalized force and a force-averaged radius, suffice to capture the overall effects of radiation forces; these combine to yield the radiation term in the virial theorem. In addition to the optically thin and thick regimes, the wavelength dependence of dust opacity allows for an intermediate case in which starlight is easily trapped but infrared radiation readily escapes. Scattering adds a non-negligible force in this intermediate regime. We address all three regimes analytically and provide approximate formulae for the force parameters, for arbitrary optical depth and inner dust temperature. Turning to numerical codes, we examine the convergence properties of the Monte Carlo code Hyperion run in Cartesian geometry. We calibrate both Hyperion and our analytical estimate using the DUSTY code, run in spherical geometry. We find that Monte Carlo codes tend to underestimate the radiation force when the mean free path of starlight is not well resolved, as this causes the inner dust temperature, and therefore the inner Rosseland opacity, to be too low. We briefly discuss implications for more complicated radiation transfer problems.

arXiv comment10 pages, 5 figures, 6 tables, accepted to MNRAS, comments welcome; updates posting from the previous "submitted to MNRAS" version, incorporating revisions suggested by the reviewer

References in corpus (21)

• Interstellar Dust Grains
• Stellar Feedback in Galaxies and the Origin of Galaxy-scale Winds
• The Disruption of Giant Molecular Clouds by Radiation Pressure and the Efficiency of Star Formation in Galaxies
• Scattering by Interstellar Dust Grains. II. X-Rays
• Self-similarity and scaling behavior of IR emission from radiatively heated dust: I. Theory
• Physical structure and CO abundance of low-mass protostellar envelopes
• The Physical Conditions for Massive Star Formation: Dust Continuum Maps and Modeling
• Structure and Evolution of the Envelopes of Deeply Embedded Massive Young Stars
• The Dynamics of Radiation Pressure-Dominated HII Regions
• Radiation pressure from massive star clusters as a launching mechanism for super-galactic winds
• HYPERION: An open-source parallelized three-dimensional dust continuum radiative transfer code
• What Drives the Expansion of Giant HII Regions?: A Study of Stellar Feedback in 30 Doradus
• Three-dimensional simulation of massive star formation in the disk accretion scenario
• Stellar Feedback in Molecular Clouds and its Influence on the Mass Function of Young Star Clusters
• On Radiation Pressure in Static, Dusty HII Regions
• Tracing the Mass during Low-Mass Star Formation. III. Models of the Submillimeter Dust Continuum Emission from Class 0 Protostars
• An Unstable Truth: How Massive Stars get their Mass
• Ionization Parameter as a Diagnostic of Radiation and Wind Pressures in H II Regions and Starburst Galaxies
• Radiation-hydrodynamical simulations of massive star formation using Monte Carlo radiative transfer: I. Algorithms and numerical methods
• Far-Infrared Spectral Energy Distributions of Embedded Protostars and Dusty Galaxies: I. Theory for Spherical Sources
• Star cluster formation with stellar feedback and large-scale inflow

Cited by in corpus (3)

• The Elephant in the Room: The Importance of Where and When Massive Stars Form in Molecular Clouds
• Are massive dense clumps truly sub-virial? A new analysis using Gould Belt ammonia data
• Capture and Escape: The Dependence of Radiation Forces on Clumping in Dusty Envelopes