Flux densities of ultracompact H II regions at 3 millimeters

Journal Article · Mon Feb 01 04:00:00 EST 1988 · Astrophys. J.; (United States)

DOI:https://doi.org/10.1086/166040· OSTI ID:7128988

Wood, D O.S.; Churchwell, E; Salter, C J

Three-millimeter continuum observations of 33 suspected ultracompact (UC) H II regions are reported. Twenty-eight sources were detected, about half of which had not previously been observed at 3 mm. These observations demonstrate that UC H II regions are bright at millimeter wavelengths and have very high emission measures. Because of this, and because UC H II regions are often associated with diffuse free-free emission, they are more easily detected at millimeter than at centimeter wavelengths. All the sources in the sample with distance estimates correspond to ionization by O6 stars or hotter. To obtain an unbiased sample of UC H II regions ionized by a single B0 star or hotter a detection limit of about 1 mJy is required. The fraction of stellar ionizing photons absorbed by dust is typically a 0.5 or more. Some of the sources reported here are small and bright enough to serve as flux and pointing calibrators at millimeter wavelengths. 16 references.

• Research Organization: Washburn Observatory, Madison, WI (USA); Instituto de Radioastronomia Milimetrica, Granada (Spain)
• OSTI ID: 7128988
• Journal Information: Astrophys. J.; (United States), Journal Name: Astrophys. J.; (United States) Vol. 325; ISSN ASJOA
• Country of Publication: United States
• Language: English

Related Subjects

640105* -- Astrophysics & Cosmology-- Galaxies
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
COSMIC DUST
COSMIC RADIO SOURCES
DUSTS
EMISSION SPECTRA
FLUX DENSITY
H2 REGIONS
IONIZATION
MICROWAVE SPECTRA
SPECTRA
STARS