The helium problem in Sagittarius B2

Details The helium problem in Sagittarius B2 The helium problem in Sagittarius B2

May 1978

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1978apj...221..810c&link_type=abstract

Astrophysical Journal, Part 1, vol. 221, May 1, 1978, p. 810-815.

Astronomy and Astrophysics

Astronomy

16

Galactic Nuclei, Helium Ions, Nebulae, Radiative Recombination, Radio Sources (Astronomy), Abundance, Astronomical Spectroscopy, H Ii Regions, Milky Way Galaxy, Radio Spectra, Thermodynamic Equilibrium

Scientific paper

The helium problem in the ionized gas of Sgr B2 is investigated by analyzing measurements of the H65-alpha, He65-alpha, C65-alpha, H92-alpha, He92-alpha, C92-alpha, H110-alpha, and He110-alpha radio recombination lines emitted from that H II region. The measurements were performed with telescope beamwidths of 1.3 to 6.5 arcmin and cover the frequency range from 4.9 to 23.4 GHz. An attempt is made to distinguish between a stimulated-emission model and a dust-absorption model by determining whether the observed values of the ionized helium-to-hydrogen number-density abundance ratio can be made consistent with a normal helium-to-hydrogen abundance ratio of 8% to 10% by number. It is found that the observations are consistent with: (1) a dust absorptivity that increases smoothly with frequency shortward of 912 A, (2) the normal helium-to-hydrogen number-density ratio, and (3) emission from zones of ionized gas that are slightly smaller for helium than for hydrogen. An He II zone having a radius nearly 80% of the radius of the H II zone is suggested.

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