We present intermediate-resolution ( R \sim 1000 ) spectra in the \sim 3 500-10 000 Å 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 CaII-triplet index in the near-infrared in order to infer the clusters ’ stellar population properties .
The inferred cluster ages are typically older than \sim 9 Gyr , although ages are derived with large uncertainties .
The clusters exhibit intermediate metallicities , in the range -1.2 \lesssim [ Fe/H ] \lesssim - 0.7 , and typically sub-solar [ \alpha / Fe ] ratios , with a peak at \sim - 0.4 .
These properties suggest that i ) during the first few Gyrs NGC 4449 formed stars slowly and inefficiently , with galactic winds having possibly contributed to the expulsion of the \alpha -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 under-abundant 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 NGC 4449 inside 2.88 kpc to be M ( < 2.88 kpc ) = 3.15 ^ { +3.16 } _ { -0.75 } \times 10 ^ { 9 } ~ { } M _ { \odot } .
We also report the serendipitous discovery of a planetary nebula within one of the targeted clusters , a rather rare event .