TY  - JOUR
A1  - Lopez, S.
A1  - Reimers, Dieter
A1  - Gregg, M. D.
A1  - Wisotzki, Lutz
A1  - Wucknitz, Olaf
A1  - Guzman, A.
T1  - Metal abundances in a damped Ly alpha system along two lines of sight at z=0.93
N2  - We study metal abundances in the z = 0.9313 damped Ly alpha 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(H I) = 1020.5 cm(-2) in both A and B. UV-visual Echelle Spectrograph spectra ( spectral resolution FWHM = 9.8 km s(-1)) 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 Ly alpha system A, while [Mn/H] = -0.98 and [Fe/H] > -1.32, and possibly as high as [Fe/H] approximate to -1, in damped Ly alpha 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 h(70)(-1) 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 Ly alpha 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
Y1  - 2005
SN  - 0004-637X
ER  - 
TY  - JOUR
A1  - Wucknitz, Olaf
A1  - Wisotzki, Lutz
A1  - Lopez, S.
A1  - Gregg, M. D.
T1  - Disentangling microlensing and differential extinction in the double QSO HE 0512-3329
N2  - We present the first separate spectra of both components of the small-separation double QSO HE 0512-3329 obtained with HST/STIS in the optical and near UV. The similarities especially of the emission line profiles and redshifts strongly suggest that this system really consists of two lensed images of one and the same source. The emission line flux ratios are assumed to be unaffected by microlensing and are used to study the differential extinction effects caused by the lensing galaxy. Fits of empirical laws show that the extinction properties seem to be different on both lines of sight. With our new results, HE 0512-3329 becomes one of the few extragalactic systems which show the 2175 Å absorption feature, although the detection is only marginal. We then correct the continuum flux ratio for extinction to obtain the differential microlensing signal. Since this may still be significantly affected by variability and time-delay effects, no detailled analysis of the microlensing is possible at the moment. This is the first time that differential extinction and microlensing could be separated unambiguously. We show that, at least in HE 0512-3329, both effects contribute significantly to the spectral differences and one cannot be analysed without taking into account the other. For lens modelling purposes, the flux ratios can only be used after correcting for both effects.
Y1  - 2003
ER  - 
TY  - JOUR
A1  - Gregg, M. D.
A1  - Schechter, P.
A1  - Becker, Rolf
A1  - Wisotzki, Lutz
A1  - Maza, J.
A1  - Laurent-Muehleisen, S.
A1  - White, R.
T1  - Two new high resolution surveys for lensed quasars
Y1  - 2001
SN  - 1-583-81074-9
ER  -