The photoevaporation of interstellar clouds. II. Equilibrium cometary clouds

Journal Article · Tue May 01 00:00:00 EDT 1990 · Astrophysical Journal; (USA)

DOI:https://doi.org/10.1086/168713· OSTI ID:7059869

Bertoldi, F; Mckee, C F ^[1]

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1. California Univ., Berkeley (USA)

An approximate analytic theory for the evolution of an interstellar cloud which is exposed to the ionizing radiation of a newly formed star is developed. This paper will follow the evolution of a photoevaporating cloud beyond its initial radiation-driven implosion. Under the realistic assumption of axisymmetry, the imploded cloud is shown to assume a steady, cometary shaped configuration in which the embracing ionization front balances the pressure of the neutral gas. The steady cloud configuration is determined solely by the cloud mass, the incident Lyman continuum flux, and the adiabatic index of the gas. Because of the rocket effect of the evaporating gas, the cloud is accelerated away from the ionizing star. Over a wide range of parameters, the cloud shape, its mass-loss rate, lifetime, and acceleration are computed. The characteristic rocket velocity is typically 10 km/s, but can be as low as 5 km/s, which is significantly lower than previous estimates. Magnetic fields are taken into account in an approximate way and are shown to be a significant factor for the cloud pressure support and gravitational stability. The theory is applied to the photoevaporating globules in the Rosette and Gum Nebulae. 55 refs.

• OSTI ID: 7059869
• Journal Information: Astrophysical Journal; (USA), Vol. 354; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
COSMIC GASES
EVAPORATION
INTERSTELLAR SPACE
ACCELERATION
ANALYTICAL SOLUTION
COMETS
GALACTIC EVOLUTION
GRAVITATION
H2 REGIONS
IMPLOSIONS
INTERSTELLAR MAGNETIC FIELDS
IONIZING RADIATIONS
LIFETIME
MASS
MATHEMATICAL MODELS
NEBULAE
SHAPE
STAR EVOLUTION
COSMIC RADIO SOURCES
FLUIDS
GASES
MAGNETIC FIELDS
PHASE TRANSFORMATIONS
RADIATIONS
SPACE
640105* - Astrophysics & Cosmology- Galaxies