Astrophys. J., 626, 767-775 (2005/June-3)
Metal abundances in a damped Lyα system along two lines of sight at z = 0.93.
LOPEZ S., REIMERS D., GREGG M.D., WISOTZKI L., WUCKNITZ O. and GUZMAN A.
Abstract (from CDS):
We study metal abundances in the z=0.9313 damped Lyα system observed along the two lines of sight, A and B, toward the gravitationally lensed double QSO HE 0512-3329. Spatially resolved Space Telescope Imaging Spectrograph spectra constrain the neutral-gas column density to be N(HI)=1020.5/cm2 in both A and B. UV-visual Echelle Spectrograph spectra (spectral resolution FWHM=9.8 km/s) show, in contrast, significant line-of-sight differences in the column densities of Mn II and Fe II; these are not due to observational systematics. We find that [Mn/H]=-1.44 and [Fe/H]=-1.52 in damped Lyα system A, while [Mn/H]=-0.98 and [Fe/H]>-1.32, and possibly as high as [Fe/H]~-1, in damped Lyα system B. A careful assessment of possible systematic errors leads us to conclude that these transverse differences are significant at a 5 σ level or greater. Although nucleosynthesis effects may also be at play, we favor differential dust depletion as the main mechanism producing the observed abundance gradient. The transverse separation is 5 h–170kpc at the redshift of the absorber, which is also likely to be the lensing galaxy. The derived abundances therefore probe two opposite sides of a single galaxy hosting both damped Lyα systems. This is the first time firm abundance constraints have been obtained for a single damped system probed by two lines of sight. The significance of this finding for the cosmic evolution of metals is discussed.
Cosmology: Observations - Galaxies: Abundances - Galaxies: Intergalactic Medium - Galaxies: Quasars: Absorption Lines - Galaxies: Quasars: Individual: Alphanumeric: HE 0512-3329
[LRG2005] DLA A (Nos A-B).
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