Microwave spectroscopic mapping of gaseous nebulae. I. Excited hydrogen, helium, and carbon in Orion B

Journal Article · Fri Jun 15 04:00:00 EDT 1973 · Astrophys. J., v. 182, no. 3, pp. 767-780

DOI:https://doi.org/10.1086/152182· OSTI ID:4317312

Chaisson, E J

Microwave (7.8-GHz) recombination lines of several excited species have been observed throughout the radio nebula Ori B. In the hydrogen line, the 94 alpha transition is mapped at eight locations and the 148 delta line is accurately observed at the position of peak flux density. The C94 alpha line is also detected at eight locations. The region of carbon emission is found to be extended ovcr at least 1.5. The apparent distribution of the mean value of the radial velocity implies a rotation period considerably longer for the carbon-line- forming volume than for the nebula. From a successful detection of a helium recombination line at the center of Ori B, we derive n(He/sup +/)/n(H/sup +/) = 0.02-0.03. He 94 alpha is also mapped at tw o additional nebular locations and is found to be apparently underabundant. We also find n(He/sup ++/)/n(H/sup +/) to be less than ~0.01. The observations, however, are consisteni with normal helium abundance (~0.09) if the volume of the He II zone is about one-third that of the H II zone. Indeed, two exciting stars of spectra type perhaps as late as 08.5 would be sufficient to ionize the helium to the extent observed in the east- west direction, and would provide a luminosity sufficent to explain the radio continuum measurements of thermal bremsstrahlung. (auth)

• Research Organization: Smithsonian Astrophysical Observatory and Harvard College Observatory, Cambridge, Massachusetts
• Sponsoring Organization: USDOE
• NSA Number: NSA-29-021952
• OSTI ID: 4317312
• Journal Information: Astrophys. J., v. 182, no. 3, pp. 767-780, Journal Name: Astrophys. J., v. 182, no. 3, pp. 767-780; ISSN ASJOA
• Country of Publication: United States
• Language: English

Related Subjects

*CARBON-- NEBULAE
*COSMIC RADIO SOURCES-- BREMSSTRAHLUNG
*HELIUM-- NEBULAE
*NEBULAE-- CHEMICAL COMPOSITION
IONIZATION
N56300* --Physics (Astrophysics & Cosmology)--Quasi-stellar
Radio & X-Ray Sources
RADIOWAVE RADIATION
STARS