Abstract
The 36. 5-GHz (H, He)56α and 22. 4-GHz (H. HE)66α radio recombination lines have been observed in the DR21 with RT22(FIAN). These data combined with the other show that the measured relative abundance y+ of ionized helium appears to increase with the angular beamwidth, ϕA, peaking at ϕA = 2‘–2. 5‘, and then to decrease as ϕA further increases what is more complicated than in previous papers. This behaviour is interpreted as a blister-type model nebula which implies the high actual helium abundance y0 =(26±11)% in the DR21 and its expansion rate from 5km s-1 to 20km s-1 by approaching the observed increasing of the hydrogen radial velocity with the frequency decreasing. Discussion has concerned slightly the explanation possibilities of the high helium abundance too.
This is a preview of subscription content, log in via an institution.
Buying options
Tax calculation will be finalised at checkout
Purchases are for personal use only
Learn about institutional subscriptionsPreview
Unable to display preview. Download preview PDF.
References
Barcia A., Gomez-Gonzalez J., Lockman F.E.,and Planesas P. (1985) ‘Radio recombination lines from the galactic plane in Cygnus’ Astr. Ap. 147, 237–240.
Churchwell E. and Mezger P. G., Huchtmeier W. (1974) ‘Helium abundance in galactic HII regions’, Astr. Ap. 32, 283–308.
Churchwell E.,Smith L.E., Mathis J., Mezger P.C., and Huchtmeier W. (1978) ‘Gradient of НII region electron temperatures and helium abundance in the Galaxy’, Astr.Ap. 70, 719–732.
Copetti M. V. F. and Bica L. D. (1983) ‘The volumes of He+ and H+ in HI I regions: the Orion Nebula’, Ap. Space Sci. 91, 381–394.
Dent W. A. (1972) ‘A flux-density scale for microwave frequecies’ Ap. J. 177, 93–99.
Dickel H.R., Goss W. M., Rots A. H., and Blount H. M. (1986) ‘VLA observations of the 6 cm and 2 cm lines of H2CO in the direction of DR21’, Astr.Ap. 162, 221–231.
Dickel H.R., Lubenow A. F., Goss W. M., Forster J. R., and Rots A. H.(1983) ‘VLA observations of H2CO in DR21’, Astr. Ap. 120, 74–84.
Goudis С (1976) ‘The radio and infrared spectrum of DR21’, Ap. Space Sci. 39, L1–L6.
Guilloteau S., Wilson T. L., Mart in R.N., Batria W., and Pauls T. A. (1983) ‘Ammonia toward DR21: a weak maser in ortho-NH3?’, Astr. Ap. 124, 322–325.
Harris S.(1973) ‘5 GHz observations of small-scale structure in DR21’, M. N.R. A.S. 162, 5p–10p.
Lichten S. M., Rodrigues L.F.,and Chaisson E.J. (1979) ‘A hydrogen and helium radio recombination-line survey of galactic HII regions at 10 GHz’, Ap. J. 229, 524–532.
Lockman F.J. and Brown R. L.(1982) ‘A survey of ionized helium in galactic HII regions’, Ap. J. 259, 595-606.
Matsumoto T.,Hayakawa S., Matsuo H., Murakami H., and Sato S. (1988) ‘The submillimeter spectrum of the cosmic background radiation’, Ap. J. 329, 567–571.
Pankonin V., Thomasson P., and Barsuhn J.(1977) ‘A survey of radio recombination lines from HI regions and associated HII regions’, Astr. Ap. 54, 335–344.
Pitault A.(1980) ‘The “helium problem” in the source DR21’, Astr. Ap. 91, 374–375.
Roelfsema P. R.(1987) ‘Radio recombination line observations of HII regions and planetary nebulae’, Ph.D. thesis. University of Groningen.
Roelfsema P. R., Goss W. M., Whiteoak J. T., Gardner F.F., and Pankonin., (1987) ‘VLA hydrogen and helium 76a radio recombination line observations of Sgr B2’, Astr. Ap. 175, 219–230.
Ryle M. and Downes D.(1967) ‘High-resolution radio observations of an intense HII region in Cygnus X’, Ap. J. 148, L17–L21(345–349).
Smirnov G.T.(1985) ‘Electron density in the HII regions DR21 and W3 from Stark broadened radio recombination lines’, Sov. Astron. Lett. 11(1), 7–11.
Thum C., Mezger P. G., and Pankonin V.(1980) ‘The helium abundance of galactic HII regions’, Astr. Ap. 87, 269–275.
Tsivilev A. P., Ershov A. A., Smirnov G.T.,and Sorochenko R. L. (1986) ‘The Orion A helium abundance’, Sov. Astron. Lett. 12, 355–359.
Vallee J. P. (1987) ‘The neutral interface adjoining the HII region DR21’, Ap. Space Sci. 129, 339–351.
Yoshioka S. and Ikeuchi S.(1987) ‘On the origin of possible deviation from the blackbody spectrum of the cosmic microwave background radiation. Inverse Compton hypothesis based upon the explosion scenario’, Ap. J. 323, L7–L11.
Zel’dovich J.B., Novikov I. D. (1975) ‘The structure and evolution of Universe’, “Science” Publisher, Moscow.
Author information
Authors and Affiliations
Editor information
Editors and Affiliations
Rights and permissions
Copyright information
© 1990 Kluwer Academic Publishers
About this chapter
Cite this chapter
Tsivilev, A.P. (1990). The Helium Abundance in the HII Region DR21. In: Gordon, M.A., Sorochenko, R.L. (eds) Radio Recombination Lines: 25 Years of Investigation. Astrophysics and Space Science Library, vol 163. Springer, Dordrecht. https://doi.org/10.1007/978-94-009-0625-9_12
Download citation
DOI: https://doi.org/10.1007/978-94-009-0625-9_12
Publisher Name: Springer, Dordrecht
Print ISBN: 978-94-010-6768-3
Online ISBN: 978-94-009-0625-9
eBook Packages: Springer Book Archive