Champagne Flow Research Articles

Cometary compact H II regions are stellar-wind bow shocks

Comet-shaped H II regions, like G34.3 + 0.2, are easily explained as bow shocks created by wind-blowing massive stars moving supersonically through molecular clouds. The required velocities of the stars through dense clumps are less than about 10 km/s, comparable to the velocity dispersion of stars in OB associations. An analytic model of bow shocks matches the gross characteristics seen in the radio continuum and the velocity structure inferred from hydrogen recombination and molecular line observations. The champagne flow model cannot account for these structures. VLBI observations of masers associated with the shells of cometary compact H II regions should reveal tailward proper motions predominantly parallel to the shell, rather than perpendicular. It is predicted that over a decade baseline, high signal-to-noise VLA observations of this class of objects will show headward pattern motion in the direction of the symmetry axis, but not expansion. Finally, shock-generated and coronal infrared lines are also predicted.

Multispectral observations of FIRSSE sources. I - Radio observations of optically identified objects

view Abstract Citations (13) References (6) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Multispectral observations of FIRSSE sources. I. Radio observations of optically identified objects. Albert, C. E. ; Schwartz, P. R. ; Bowers, P. F. ; Rickard, L. J. Abstract Very Large Array radio maps of eight H II regions detected in the AFGL/NRL Far Infrared Sky Survey Experiment (FIRSSE) are compared to their optical images. The radio morphologies are consistent with "champagne flows". Infrared Astronomical Satellite (IRAS) photometry shows that all of these objects have luminosities which are less than or comparable to those of zero-age main-sequence stars. Publication: The Astronomical Journal Pub Date: July 1986 DOI: 10.1086/114136 Bibcode: 1986AJ.....92...75A Keywords: Astronomical Maps; Infrared Astronomy; Radio Sources (Astronomy); Far Infrared Radiation; H Ii Regions; Morphology; Optical Measurement; Sky Surveys (Astronomy); Stellar Luminosity; Stellar Temperature; Very Large Array (Vla); Astrophysics full text sources ADS | data products SIMBAD (7)

Shell structure in ultracompact H II regions

view Abstract Citations (91) References (42) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Shell structure in ultracompact H II regions. Turner, B. E. ; Matthews, H. E. Abstract Very Large Array observations of six ultracompact H II regions made at 2 cm wavelength and with high angular resolution (about 0.1 arcsec) have revealed shell or ring structures on the size scale 0.02-0.1 pc in four of the objects. Electron densities are of order 10 to the 5th per cu cm, and emission measures are about 10 to the 8th-10 to the 9th pc per cm to the 6th. The contrast ratio for at least one of the four sources is excessive for a uniform shell and suggests ringlike structure. These structures have been analyzed in terms of cocoon models, stellar winds, and champagne flows. The observed sources do not appear inconsistent with modified stellar wind models. It is less clear whether cocoon models are consistent with the present observations. They are not consistent with the more fundamental morphological characteristics of champagne flows. Publication: The Astrophysical Journal Pub Date: February 1984 DOI: 10.1086/161679 Bibcode: 1984ApJ...277..164T Keywords: H Ii Regions; Interstellar Gas; Radio Astronomy; Ring Structures; Stellar Envelopes; Stellar Winds; Brightness Temperature; Bubbles; Interferometry; Radiant Flux Density; Stellar Evolution; Very Large Array (Vla); Astrophysics full text sources ADS | data products SIMBAD (8)

A study of H-alpha velocities in NGC 1499, NGC 7000, and IC 1318B/C

Multiple slit echelle spectrograph observations of the H-alpha emission line are used to map the radial velocities of the California Nebula (NGC 1499), the North American Nebula complex (NGC 7000 and IC 5070), and IC 1318B/C. The California Nebula is singularly constant in velocity, considering its geometry. The North American Nebula complex reflects a very simple, classical dynamical picture. The expansion discovered earlier in IC 1318B/C is confirmed, detailed, and the model refined. The new data, along with that in earlier papers of this series, show that stellar wind acceleration and champagne flow mechanisms both play important roles in determining the evolution of H II regions.

The gas dynamics of H II regions. II - Two-dimensional axisymmetric calculations

view Abstract Citations (240) References (19) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The gas dynamics of H II regions. II. Two-dimensional axisymmetric calculations. Bodenheimer, P. ; Tenorio-Tagle, G. ; Yorke, H. W. Abstract Hydrodynamic numerical calculations of the evolution of H II regions in dense molecular clouds are extended to two space dimensions with axial symmetry. Specific problems are treated which emphasize the behavior of flows that cross a discontinuity between a cloud and the low-density intercloud medium. Calculations are performed for four cases, including two involving 'champagne flows': (1) the edge of the cloud is overrun by a supersonic ionization front; (2) the initial Stromgren sphere surrounding the star lies deep inside the cloud, so that the cloud's edge is ionized by a subsonic ionization front; (3) the ionization front breaks through two opposite faces of the same cloud simultaneously; and (4) the flow encounters an isolated globule with a density of 1000 particles/cu cm shortly after emerging from the molecular cloud. The results are compared with observations of various interstellar clouds. Publication: The Astrophysical Journal Pub Date: October 1979 DOI: 10.1086/157368 Bibcode: 1979ApJ...233...85B Keywords: Astronomical Models; Gas Dynamics; H Ii Regions; Interstellar Matter; Nebulae; Stellar Evolution; Gas Ionization; Graphs (Charts); Hydrodynamic Equations; Hydrodynamics; Mathematical Models; Tables (Data); Astrophysics; H II Regions:Evolution; H II Regions:Gas Dynamics full text sources ADS |