LBT/MODS spectroscopy of globular clusters in the irregular galaxy NGC 4449

We present intermediate-resolution (R similar to 1000) spectra in the similar to 3500-10 000 angstrom range of 14 globular clusters in the Magellanic irregular galaxy NGC 4449 acquired with the Multi-Object Double Spectrograph on the Large Binocular Telescope. We derived Lick indices in the optical and the Ca II triplet index in the near-infrared in order to infer the clusters' stellar population properties. The inferred cluster ages are typically older than similar to 9 Gyr, although ages are derived with large uncertainties. The clusters exhibit intermediate metallicities, in the range -1.2 less than or similar to [Fe/H] less than or similar to -0.7, and typically sub-solar [alpha/Fe] ratios, with a peak at similar to-0.4. These properties suggest that (i) during the first few Gyr NGC 4449 formed stars slowly and inefficiently, with galactic winds having possibly contributed to the expulsion of the a-elements, and (ii) globular clusters in NGC 4449 formed relatively 'late', from a medium already enriched in the products of Type Ia supernovae. The majority of clusters appear also underabundant in CN compared to Milky Way halo globular clusters, perhaps because of the lack of a conspicuous N-enriched, second generation of stars like that observed in Galactic globular clusters. Using the cluster velocities, we infer the dynamical mass of NGC4449 inside 2.88 kpc to be M(< 2.88 kpc) = 3.15(-0.75)(+3.16) x 10(9) M-circle dot. We also report the serendipitous discovery of a planetary nebula within one of the targeted clusters, a rather rare event.