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 Abell3389 (z ~ 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 α-abundance. Generally, the galaxies in our sample have flat radial trends in age and [α/Fe], but negative gradients in [Z/H] (-0.20 +/- 0.05dex). 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 >4σ), such that galaxies with young cores have steeper positive age gradients, and those with metal-rich centres have strong negative [Z/H] gradients.

Based on observations collected at the European Organisation for Astronomical Research in the Southern Hemisphere, Chile (run: 078.B-0539).

E-mail: t.d.rawle@durham.ac.uk