Metal Abundances in a Damped LyA System Along Two Lines of Sight at z=0.93
DOI: 10.1086/429956 (http) or 10.1086/429956 (doi)
ADS bibcode 2005ApJ...626..767L
astro-ph/0503026
Sebastian Lopez [1], Dieter Reimers [2], Michael D. Gregg [3,6], Lutz Wisotzki [4], Olaf Wucknitz [5], and Andres Guzman [1]
- Departamento de Astronomia, Universidad de Chile, Casilla 36-D, Santiago, Chile
- Hamburger Sternwarte, Gojenbergsweg 112, D-21029 Hamburg, Germany
- Physics Department, University of California, Davis, CA 95616
- Astrophysikalisches Institut Potsdam, An der Sternwarte 16, D-14482 Potsdam, Germany
- Institut fuer Physik, Universitaet Potsdam, Am Neuen Palais, D-14469 Potsdam, Germany
- Institute of Geophysics & Planetary Physics, Lawrence Livermore National Laboratory, Livermore, CA 94550
Abstract
We study metal abundances in the z=0.9313 damped Lya system observed in the two lines-of-sight, A and B, toward the gravitationally-lensed double QSO HE0512-3329. Spatially resolved STIS spectra constrain the neutral-gas column density to be LogN(HI)=20.5 in both Aand B. UVES spectra (spectral resolution FWHM=9.8 km/s) show, in contrast, significant line-of-sight differences in the column densities of MnII and FeII; these are not due to observational systematics. We find that [Mn/H]=-1.44 and [Fe/H]=-1.52 in damped Lya system A, while [Mn/H]=-0.98 and [Fe/H]>-1.32, and possibly as high as [Fe/H] approx. -1 in damped Lya system B. A careful assessment of possible systematic errors leads us to conclude that these transverse differences are significant at a 5 sigma 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 kpc 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 Lya 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.
Key words:
cosmology: observations -- galaxies: abundances -- intergalactic medium -- quasars: absorption lines -- quasars: individual (HE0512-3329)
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ApJ 626 (2005) 767 (link to online journal)
DOI (Digital Object Identifier): 10.1086/429956 (http) or 10.1086/429956 (doi)
ADS bibcode 2005ApJ...626..767L (link to ADS entry)
astro-ph/0503026 (link to e-print archive)
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ApJ version, 9 pages
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