2009MNRAS.399L.103G

We employ three samples of nearby stars that include stars hosting Doppler-detected planets to test a recent finding by Haywood that the incidence of planets is greater among transition and thick disc stars than it is among thin disc stars in the range [Fe/H] ≤ -0.20 dex; this implies that distance from the Galactic Centre is the causative factor for planet formation, not [Fe/H]. Thick disc stars with planets do have a smaller mean [Fe/H] value than thin disc stars over this range in [Fe/H], and the most [Fe/H]-poor stars with planets tend to have more negative V_lsrvalues. However, if we compare stars with planets according to mass abundance of the refractory elements important for planet formation (Mg, Si, Fe), then thick disc and [Fe/H]-poor thin disc stars with planets have similar distributions. There is no need to invoke a new mechanism for giant planet formation to account for the distributions of stars with planets among dwarf stars.