We investigate radial and vertical metallicity gradients for a sample of red clump stars from the RAdial Velocity Experiment ( RAVE ) Data Release 3 .
We select a total of 6781 stars , using a selection of colour , surface gravity and uncertainty in the derived space motion , and calculate for each star a probabilistic ( kinematic ) population assignment to a thin or thick disc using space motion and additionally another ( dynamical ) assignment using stellar vertical orbital eccentricity .
We derive almost equal metallicity gradients as a function of Galactocentric distance for the high probability thin disc stars and for stars with vertical orbital eccentricities consistent with being dynamically young , e _ { v } \leq 0.07 , i.e . d [ M / H ] / dR _ { m } = -0.041 \pm 0.003 and d [ M / H ] / dR _ { m } = -0.041 \pm 0.007 dex kpc ^ { -1 } .
Metallicity gradients as a function of distance from the Galactic plane for the same populations are steeper , i.e . d [ M / H ] / dz _ { max } = -0.109 \pm 0.008 and d [ M / H ] / dz _ { max } = -0.260 \pm 0.031 dex kpc ^ { -1 } , respectively . R _ { m } and z _ { max } are the arithmetic mean of the perigalactic and apogalactic distances , and the maximum distance to the Galactic plane , respectively .
Samples including more thick disc red clump giant stars show systematically shallower abundance gradients .
These findings can be used to distinguish between different formation scenarios of the thick and thin discs .