Probing Spectral Line Gradients beyond One Effective Radius in NGC 3610

The outer region (0.75--1.25 r_e in the B-band) of the merger-remnantelliptical NGC 3610 is studied using extremely high signal to noise Keckspectra, with a supplementary spectrum of the galaxy center. Stellar populationparameters -- age, [Z/H], [$\alpha$/Fe] -- are measured in several aperturesalong the slit. Using the multi-index simultaneous fitting method of Proctor etal. (2004), no significant stellar population gradients are detected in theouter parts of the galaxy. The overall gradients relative to the galaxy centerare consistent with those found in many other early-type galaxies, though themetallicity gradient is much steeper than would be expected if NGC 3610 formedin a major merger event. Standard analysis methods using the H$\beta$ index arefound to produce spurious radially variable gradients.Comment: 15 pages, 9 figures, accepted by A