Abstract
view Abstract Citations (83) References (20) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Detection of 21-cm absorption at z ≈ 1.8 in the quasi-stellar object 1331+170. Wolfe, A. M. ; Davis, M. M. Abstract The detection of 21-cm absorption by neutral hydrogen in front of the QSO 1331+170 is reported. The line arises at 511.596 + or - 0.005 MHz, corresponding to a redshift, z=1.77642 + or - 0.00002, that is identical, within observational errors, to the previously detected optical redshift of absorption system A. The coincidence between radio and optical redshifts yields the strictest limit ever placed on the variation of certain physical constants over a look-back time comprising at least 65% of the current age of the universe, if the redshifts are cosmological. Comparison with a similar limit pertaining to the z=0.524 absorption event in AO 0235+164 indicates that physical constants in two globally separated regions also coincide. This is evidence for large-scale invariance of physical laws. An analysis of the L-alpha and 21-cm absorption data results in the determination of the spin temperature in a high-z object. If confirmed by future tests, the spin temperature of approximately 1000 K would imply a difference between H I in our Galaxy and in the absorber at z of approximately 1.8. Publication: The Astronomical Journal Pub Date: June 1979 DOI: 10.1086/112470 Bibcode: 1979AJ.....84..699W Keywords: Astronomical Spectroscopy; Electromagnetic Absorption; Neutral Gases; Quasars; Radio Astronomy; Absorption Spectra; Centimeter Waves; Hydrogen Clouds; Lyman Alpha Radiation; Red Shift; Spin Temperature; Astrophysics; Neutral Hydrogen:Quasars full text sources ADS | data products SIMBAD (4) NED (1)
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