Abstract
Sensitive spectral observations made in two frequency bands near 6.0 and 17.6 GHz are described for Orion and W51. Using frequency switching we were able to achieve a dynamic range in excess of 10,000 without fitting sinusoidal or polynomial baselines. This enabled us to detect lines as weak as T A ∼1 mK in these strong continuum sources. Hydrogen recombination lines with Δn as high as 25 have been detected in Orion. In the Orion data, where the lines are stronger, we have also detected a systematic shift in the line center frequencies proportional to linewidth that cannot be explained by normal optical depth effects.
This is a preview of subscription content, log in via an institution to check access.
Similar content being viewed by others
References
Balser, D.S., Bania, T.M., Brockway, C.J., Rood, R.T., Wilson, T.L.: Astrophys. J. 430, 667 (1994)
Bania, T.M., Rood, R.T., Wilson, T.L.: Astrophys. J. 323, 30 (1987)
Bell, M.B.: Astrophys. J. 453, 773 (1995)
Bell, M.B.: Publ. Astron. Soc. Pac. 109, 609 (1997)
Bell, M.B., Feldman, P.A.: Astrophys. J. 367, L33 (1991)
Bell, M.B., Avery, L.W., Seaquist, E.R., Vallée, J.P.: Publ. Astron. Soc. Pac. 112, 1236 (2000)
Carrington, A., Leach, C.A., Moss, R.K., Steimle, T.C., Viant, M.R., West, Y.D.: J. Chem. Soc. Faraday Trans. 89(4), 603 (1993)
Churchwell, E.: Astron. Astrophys. 15, 90 (1971)
Davies, R.D.: Astrophys. J. 163, 479 (1971)
Griem, H.R.: Astrophys. J. 148, 547 (1967)
Griem, H.R.: Spectral Line Broadening by Plasmas. Academic Press, New York (1974)
Gordon, M.A.: In: Spectral Line Shapes, 19th International Conf. on Spectral Lines, Valladolid, Spain. AIP Conference Proceedings, vol. 1058, p. 273 (2008)
Hansen, S.S., Johnston, K.J.: Astrophys. J. 267, 625 (1983)
Lockman, F.J., Brown, R.L.: Astrophys. J. 201, 134 (1975)
Peimbert, M., Rodriguez, L.F., Bania, T.M., Rood, R.T., Wilson, T.L.: Astrophys. J. 395, 484 (1992)
Rood, R.T., Bania, T.M., Wilson, T.L.: Astrophys. J. 280, 629 (1984)
Smirnov, G.T., Sorochenko, R.L., Pankonin, V.: Astron. Astrophys. 135, 116 (1984)
Author information
Authors and Affiliations
Corresponding author
Rights and permissions
About this article
Cite this article
Bell, M.B., Avery, L.W., MacLeod, J.M. et al. Sensitive observations of radio recombination lines in Orion and W51: the data and detection of systematic recombination line blueshifts proportional to impact broadening. Astrophys Space Sci 333, 377–388 (2011). https://doi.org/10.1007/s10509-011-0662-5
Received:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1007/s10509-011-0662-5