Line-Strength Gradients in NGC 5813

Abstract
We have measured line-strength gradients out to 80 arcsec from the centre of the elliptical galaxy NGC 5813. The line-strength measures include the Mg2 index and the equivalent widths of Hβ and two iron blends at 5270 and 5335 Å. Our results show that Mg2 falls from 0.31 in the nucleus to ≲0.1 in the outer parts of this galaxy and, for the first time, we have detected gradients in the iron features. In the halo of NGC 5813 the strengths of all the features considered here, including Hβ and the iron lines, match those of Galactic globular clusters at similar values of Mg2. The results suggest, with little ambiguity, that the metallicity in this galaxy falls from [Fe/H]>0 in the centre, to [Fe/H]∼−0.7 in the outer parts.

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