Section 6.1 For a discussion of the isotopic ratios of CO, see
Langer, W. D. 1997, in CO: Twenty-Five Years of Millimeter-Wave Spectroscopy, ed. W. B. Latter, S. J. E. Radford, P. R. Jewell, J. G. Magnum, and J. Bally (Dordrecht: Kluwer), p. 98.
Application of the detection equation to observations of both CO and NH3 is covered in
Martin, R. N. & Barrett, A. H. 1978, ApJSS, 36, 1. The Nh-Av correlation was first obtained by
Bohlin, R. C., Savage, B. D., & Drake, J. F. 1978, ApJ, 224, 132. while the NCO-Av and NCO-Nh relations are due to
Dickman, R. L. 1978, ApJSS, 37, 407. The proportionality constant X between NH and the integrated 12C16O intensity is a central topic in
Section 6.2 The analysis of NH3 hyperfine transitions is presented in
Barrett, A. H., Ho, P. T. P., & Myers, P. C. 1977, ApJ, 211, L39, and applied extensively to dense cores by
Jijina, J., Myers, P. C., & Adams, F. C. 1999, ApJSS, 125, 161. For a critical discussion of the standard interpretation of NH3 spectra, see Stutzki, J. & Winnewisser, G. 1985, AA, 148, 254.
Section 6.3 The physics of the Zeeman effect is lucidly explained in
Powell, J. L. & Crasemann, B. 1961, Quantum Mechanics (Reading: Addison-Wesley), Chapter 10.
The first detection of the effect in molecular clouds was due to
Crutcher, R. M. & Kazes, I. 1983, AA, 125, L23. Reviews of subsequent observations, using OH and other tracers, are in Crutcher, R. M. 1999, ApJ, 520, 706
Bourke, T. L., Myers, P. C., Robinson, G., & Hyland, A. R. 2001, ApJ, 554, 916.
The Formation of Stars
Steven W. Stahler and Francesco Palla © 2004 WILEY-VCH Verlag GmbH & Co.
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