FIG. 1: (Left) Hubble Space Telescope color composite image of the Clone arc. A1-5 represent multiple images of the z=2.00 source; the critical curve is shown in red. The OSIRIS pointings are indicated by the two green rectangles offset by 1.8 arcseconds in the East-West direction. Foreground lensing galaxies are labeled as G1-4. (Right) Distribution of the key emission line fluxes in multiple images A3-5 in units of 10−18 erg/s/cm2 (see text for discussion of optimum samplig). North is up and East is to the left. The critical line passes through the A3 and A4 components such that a small part of the arc (including A5) is imaged 4 times in the OSIRIS field. The remainder of A3/A4 is imaged twice in the OSIRIS field.
From these and other results they conclude:
We find a strong radial gradient in both the [Nii]/H and [Oiii]/H ratios indicating a metallicity gradient of −0.27±0.05 dex kpc−1 with central metallicity close to solar. This suggests that subsequent growth occurs in an inside-out manner with the inner metallicity gradient diminished over time due to radial mixing and enrichment from star formation.
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