We present radial velocities and [ Fe/H ] abundances for 340 stars in the Fornax dwarf spheroidal from R \sim 16 , 000 spectra .
The targets have been obtained in the outer parts of the galaxy , a region which has been poorly studied before .
Our sample shows a wide range in [ Fe/H ] , between -0.5 and -3.0 dex , in which we detect three subgroups .
Removal of stars belonging to the most metal-rich population produces a truncated metallicity distribution function that is identical to Sculptor , indicating that these systems have shared a similar early evolution , only that Fornax experienced a late , intense period of star formation ( SF ) .
The derived age-metallicity relation shows a fast increase in \mathrm { [ Fe / H ] } at early ages , after which the enrichment flattens significantly for stars younger than \sim 8 Gyr .
Additionally , the data indicate a strong population of stars around 4 Gyr , followed by a second rapid enrichment in [ Fe/H ] .
A leaky-box chemical enrichment model generally matches the observed relation but does not predict a significant population of young stars nor the strong enrichment at late times .
The young population in Fornax may therefore originate from an externally triggered SF event .
Our dynamical analysis reveals an increasing velocity dispersion with decreasing [ Fe/H ] from \sigma _ { sys } \approx 7.5 \mathrm { kms ^ { -1 } } to \geq 14 , \mathrm { kms ^ { -1 } } , indicating an outside-in star formation history in a dark matter dominated halo .
The large velocity dispersion at low metallicities is possibly the result of a non-Gaussian velocity distribution amongst stars older than \sim 8 Gyr .
Our sample also includes members from the Fornax GCs H2 and H5 .
In agreement with past studies we find \mathrm { [ Fe / H ] } = -2.04 \pm 0.04 and a mean radial velocity RV = 59.36 \pm 0.31 \mathrm { km s ^ { -1 } } for H2 and \mathrm { [ Fe / H ] } = -2.02 \pm 0.11 and RV = 59.39 \pm 0.44 \mathrm { km s ^ { -1 } } for H5 .
Finally , we test different calibrations of the Calcium Triplet over more than 2 dex in \mathrm { [ Fe / H ] } and find best agreement with the calibration equations provided by Carrera et al .
( 19 ) .
Overall , we find large complexity in the chemical and dynamical properties , with signatures that additionally vary with galactocentric distance .
Detailed knowledge about the properties of stars at all radii is therefore necessary to draw a conclusive picture about the star formation and chemical evolution in Fornax .