We present the first determination of the radial velocities and metallicities of 78 red giant stars in the isolated dwarf irregular galaxy WLM .
Observations of the calcium II triplet in these stars were made with FORS2 at the VLT-UT2 in two separated fields of view in WLM , and the [ Fe/H ] values were conformed to the ( 14 ) ( [ Fe/H ] _ { CG 97 } ) metallicity scale .
The mean metallicity is \langle [ Fe/H ] \rangle = -1.27 \pm 0.04 dex , with a standard deviation of \sigma = 0.37 .
We find that the stars in the inner field are more metal rich by \Delta [ Fe/H ] = 0.30 \pm 0.06 dex .
These results are in agreement with previous photometric studies that found a radial population gradient , as well as the expectation of higher metallicities in the central star forming regions .
Age estimates using Victoria-Regina stellar models show that the youngest stars in the sample ( < 6 Gyr ) are more metal rich by \Delta [ Fe/H ] = 0.32 \pm 0.08 dex .
These stars also show a lower velocity dispersion at all elliptical radii compared to the metal-poor stars .
Kinematics for the whole red giant sample suggest a velocity gradient approximately half that of the gas rotation curve , with the stellar component occupying a thicker disk decoupled from the HI rotation plane .
Taken together , the kinematics , metallicities , and ages in our sample suggest a young metal-rich , and kinematically cold stellar population in the central gas-rich regions of WLM , surrounded by a separate dynamically hot halo of older , metal poor stars .