The morphologies and physical properties of ultracompact H II regions

Journal Article · Sat Apr 01 04:00:00 EST 1989 · Astrophys. J., Suppl. Ser.; (United States)

DOI:https://doi.org/10.1086/191329· OSTI ID:5856273

Wood, D O.S.; Churchwell, E

Seventy-five ultracompact (UC) H II regions are observed 0.4 arcsec resolution at 2 and 6 cm using the Very Large Array, and their radio continuum brightness distributions are presented in the form of contour plots. H-76 alpha recombination line profiles are obtained for six sources using a 4.4 arcsec beam. It is shown that these UC H II regions have electron densities of at least approximately 10,000 per cubic cm, emission measures of at least approximately 10 to the 7th pc cm to the -6th, and diameters no more than approximately 0.1 pc, consistent with their being small photoionized nebulae produced by O and B stars embedded in clouds of molecular gas and dust. At high angular resolution five different morphologies of the ionized gas are seen: spherical or unresolved (43 percent), cometary (20 percent), core-halo (16 percent), shell (4 percent), and irregular or multiply peaked (17 percent). Evidence is presented that the UC H II region phase of a massive star must last for a significant fraction of its main-sequence lifetime. 89 refs.

• Research Organization: Washburn Observatory, Madison, WI (USA)
• OSTI ID: 5856273
• Journal Information: Astrophys. J., Suppl. Ser.; (United States), Journal Name: Astrophys. J., Suppl. Ser.; (United States) Vol. 69; ISSN APJSA
• Country of Publication: United States
• Language: English

Related Subjects

640105* -- Astrophysics & Cosmology-- Galaxies
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
ASTRONOMY
COORDINATES
COSMIC GASES
COSMIC RADIO SOURCES
DATA ANALYSIS
ELECTROMAGNETIC RADIATION
ELECTRON DENSITY
FLUIDS
GASES
H2 REGIONS
INFRARED RADIATION
INTERSTELLAR SPACE
IONIZED GASES
MASS
MOLECULES
MORPHOLOGY
PHYSICAL PROPERTIES
RADIATIONS
RADIOASTRONOMY
RADIOWAVE RADIATION
SPACE