Stellar mass of the primary galaxy as a function of redshift for our major (top) and minor (bottom) close pair samples. Right pointing triangles correspond to close pairs in the HDF-S, other triangles to close pairs in the COSMOS-Gr30 field, squares are pairs from A2744, and circles from the UDF-Mosaic. Symbols are color-coded with respect to the weight, W_p described in Sect. 3.2.3, used for the computation of merger fractions. Darker pairs have a higher probability of merging by z = 0 and will thus have a higher contribution on the estimated merger fraction. Except in the redshift desert (z ∼ 1.5−2.8), we have a relatively good stellar mass completeness level for major close pairs down to a primary galaxy stellar mass of ≈10⁷ M_⊙. However, for the minor close pairs sample, a lower mass limit of 10⁹ M_⊙ must be applied to keep a reasonable level of completeness for the merger fraction estimates.