Astronomy and Astrophysics – Astronomy
Scientific paper
May 1999
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1999aas...194.3001k&link_type=abstract
American Astronomical Society, 194th AAS Meeting, #30.01; Bulletin of the American Astronomical Society, Vol. 31, p.867
Astronomy and Astrophysics
Astronomy
1
Scientific paper
We present high signal-to-noise ratio data on an extremely simple zabs ~ 3 partial Lyman limit absorption system. This absorber has only a single major velocity component, and unsaturated high order H I Lyman series lines. Hence, the parameters which describe the Hydrogen absorption are very well determined. We find excess absorption on the blue wing of the H I Lyalpha line, near to the expected position of deuterium absorption. The excess absorption is slight, allowing us to set a firm upper limit to the amount of deuterium absorption in this absorber, D/H < 6 x 10(-5) . However, the expected deuterium line is at the wrong wavelength to explain all of the excess absorption on the blue wing of the H I Lyalpha line, and hence there must be contamination by additional H I interloper absorption. Because the parameters of the H I interloper and the D line will be somewhat degenerate, we can not place a lower limit on D/H in this absorption system. We show that this system probably has a very low metallicity, [C/H] < -2, so that our upper limit of D/H < 6 x 10(-5) should be representative of primordial D/H. All four of the known high redshift absorption line systems simple enough to provide useful limits on D are consistent with the low value of D/H = 3.4 +/- 0.5 x 10(-5) measured towards QSO 1009+2956 and QSO 1937-1009 by Burles and Tytler (1998a, 1998b). Conversely, three of the four D/H limits are inconsistent with high D/H value proposed by Webb et al. (1997a, 1997b) towards QSO 1718+4807.
Burles Scott
Kirkman David
Lubin Dan
Omeara J.
Tytler David
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