Stellar population gradients in early-type cluster galaxies with VIMOS IFU

We present results from a pilot study of radial stellar population trends in early-type galaxies using the Very Large Telescope (VLT) Visible Multi-Object Spectrograph (VIMOS) integral field unit (IFU). We observe 12 galaxies in the cluster Abell 3389 (z approximate to 0.027). For each galaxy, we measure 22 line strength indices in multiple radial bins out to at least the effective radius. We derive stellar population parameters using a grid inversion technique, and calculate the radial gradients in age, metallicity and alpha-abundance. Generally, the galaxies in our sample have flat radial trends in age and [alpha/Fe], but negative gradients in [Z/H] (-0.20 +/- 0.05 dex). Combining our targets with two similar, long-slit studies to increase sample size, we find that the gradients are not correlated with the central velocity dispersion or K-band luminosity (both proxies for galaxy mass). However, we find that the age and metallicity gradients are both anticorrelated with their respective central values (to > 4 sigma), such that galaxies with young cores have steeper positive age gradients, and those with metal-rich centres have strong negative [Z/H] gradients.