SPS Effects on Optical and Radio Astronomy

BALL, J. A., ZUCKERMAN, B., GOTTLIEB, C. A. and RADFORD, H. E. [1970] Bulletin of the American Astronomical Society, 2, 293. BARE, C., CLARK, B. G., KELLERMANN, K. L, COHEN, M. H. and JAUNCEY, D. L. [1967] Science, 157, 189. BOLTON, J.G., van DAMME, K. J., GARDNER, F. F. and ROBINSON, B. J. [1964a] Nature, 201, 279. BOLTON, J. G., GARDNER, F. F., McGEE, R. X. and ROBINSON, B. J. [1964b] Nature, 204, 30. BROTEN, N.W., LEGG, T.H., LOCKE, J. L„ McLEISH, C. W., RICHARDS, R. S., CHISOLM, R. M., GUSH, H. P., YEN, J. L. and GALT, J. A. [1967] Science, 156, 1592. DAVIES, R. D„ de JAEGER, G. and VERSCHUUR, G. L„ [1966] Nature, 209, 974. DAVIES, RD., ROWSON, B., BOOTH, R. S., COOPER, A. J., GENT, H., ADGIE, R. L. and CROWTHER, J. H. [1967] Nature, 213, 1109. EHRENSTEIN, G., TOWNES, C. H. and STEVENSON, M. J. [1959] Phys. Rev. Letters, 3, 40. GOLD, T. [1967] Science, 157, 302-304. GOLDSTEIN, S. J., GUNDERMANN, E. J., PENZIAS, A. A. and LILLEY, A. E. [1964] Nature, 203, 65. GOSS, W. M. [1968] Astrophys. Journ., Suppl., 15, 131. MacDONALD, G. J. F. [1967] Science, 157, 304-305. McGEE, R. X., ROBINSON, B. J., GARDNER, F. F. and BOLTON, J. G. [1965] Nature, 208, 1193. MORAN, J. M„ CROWTHER, P. P., BURKE, B. F., BARRETT, A. H., ROGERS, A. E. E„ BALL, J. A., CARTER, J. C. and BARE, C. C. [1967] Science , 157, 676. ROBINSON, B. J., GARDNER, F. F., van DAMME, K. J. and BOLTON, J. G. [1964] Nature, 202, 989. ROGERS, A. E. E. and BARRETT, A. H. [1966] Astron. Journ., 71, 868. ROGERS, A. E. E., MORAN, J. M., CROWTHER, P. P„ BURKE, B. F., MEEKS, M. L„ BALL, J. A. and HYDE, G. M. [1967] Astrophys. Journ., 147, 369. TURNER, B. E. [1970] Astrophys. Journ. (Letters), 6, 99. TURNER, B. E. [1972] Astrophys. Journ., 171, 503. TURNER, B. E„ PALMER, P. and ZUCKERMAN, B. [1970] Astrophys. Journ. (Letters), 160, L125. WEAVER, H., WILLIAMS, D. R. W„ DIETER, N. H. and LUM, W. T. [1965] Nature, 208, 29. WEINREB, S„ BARRETT, A. H., MEEKS, M. L. and HENRY, J. C. [1963] Nature, 200, 829. WEINREB, S., MEEKS, M. L„ CARTER, J. C„ BARRETT, A.H. and ROGERS, A. E. E. [1965] Nature, 208, 440. WELIZCHEW, L. [1971] Astrophys. Journ. (Letters), 167, L47. WILSON, W. J. and BARRETT, A. H. [1970] Astropys. Journ. (Letters), 6, 231. YEN, J. L., ZUCKERMAN, B., PALMER, P. and PENFIELD, H. [1969] Astrophys. Journ. (Letters), 156, L27. ZUCKERMAN, B., LILLEY, A. E. and PENFIELD, H. [1965] Nature, 208, 441. ZUCKERMAN, B., PALMER, P., PENFIELD, H. and LILLEY, A. E. [1968] Astrophys. Journ. (Letters), 153, L69. ANNEX III WATER VAPOUR LINE AT 22.235 GHz 1. Introduction The 22.235 GHz spectral line of the water molecule is well known to radio engineers because of its contribution to atmospheric absorption of radio waves. The water vapour line in the atmosphere is pressure broadened causing significant propagation loss over a band of several GHz around the 22.235 GHz centre frequency. The important possibility that water molecules in space could be detected through identification of this line was considered feasible [Snyder and Buhl, 1969], since the line width will be much narrower for molecules at very low pressure in space, and can easily be distinguished from the very broad atmospheric line. The line emission from H2O molecules in space was discovered in 1968 [Cheung et al., 1969] in three separate regions in the Galaxy, and at a suprisingly high intensity level. In fact, by orders of magnitude, the H2O sources are the most intense celestial radio sources in this frequency range, with the exception of continuous emissions from the Sun and the Moon. In rapid succession, a number of additional very intense celestial H2O sources were discovered and it was found that the sources emit complex spectra of Doppler-shifted lines; that the radiation is in some cases linearly polarized; that the sources are smaller than the beams of large radio telescopes; and that the line intensities are highly variable, in some cases over periods of a week which suggests extremely small source sizes [Knowles et al., 1969a,b; Meeks et al., 1969; Buhl et al., 1969; Turner et al., 1970; Sullivan, 1971, 1973; Johnston et al., 1971a, 1973; Turner et al., 1971]. Investigations by the technique of very long base-line interferometry have shown angular sizes for the sources as small as 0.0003 arc seconds, comparable in angular diameter with the smallest known celestial radio continuum sources [Burke et al., 1970, 1971; Johnston et al., 1971b; Abliazov et al., 1974]. Maser amplification by the water molecules is indicated by the very high line intensities and very small source

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