Optical spectra of QSO 1937-1009 (zem = 3.78, V =~ 17.5) with the W. M. Keck telescope HIRES echelle spectrograph show deuterium in the Lymanalpha and Lyman-beta lines of an absorption systems at 3.57. The H I Lyman series lines are narrow (b =~ 20 km s(-1) ) and resolved all the way to Lyman-19. They absorb all the flux in their cores, and there is strong Lyman continuum absorption, showing that the H I column density is log N(H I) >= 17.8. Weak metal lines in the system, C IV, CII, SI IV and Si II all show the same profiles which are adequately described by two clouds separated by 13 km s(-1) . A simultaneous fit all the Lyman series lines, especially the weaker high order lines, indicates a total H I column of about 10(18) , with 80% in the lower redshift component. The same fit gives D/H =~ 2 times 10(-5) (preliminary), which corresponds to a high cosmological baryon density of Omega_b =~ 0.03 h100(-2) . Both clouds are moderately ionized, with H I/H =~ 0.01. The metal abundances are about [C/H] =~ -3.1 and [Si/H] =~ -2.7 in the component with the most H I and D I, and [C/H] =~ -2.0 and [Si/H] =~ -1.7 in the other cloud. Both have [C/Si] =~ -0.3, like low abundance halo stars, and their abundances are much too low for stars to have removed significant deuterium. These results are consistent with D/H of (1 -- 2) times 10(-5) from the interstellar medium, but not with Songalia et al. (1994, Nature, 368, 599) who reported D/H = 2.6 times 10(-4) , at least ten times more D, in a different QSO absorber. Either their absorption line was H rather than D, or primordial nucleosynthesis was dramatically inhomogeneous.
American Astronomical Society Meeting Abstracts
- Pub Date:
- December 1994