The galaxy major merger fraction to z ∼ 1

Aims. The importance of disc-disc major mergers in galaxy evolution remains uncertain. We study the major merger fraction in a SPITZER/IRAC-selected catalogue in the GOODS-S field up to z similar to 1 for luminosity- and mass-limited samples. Methods. We select disc-disc merger remnants on the basis of morphological asymmetries/distortions, and address three main sources of systematic errors: (i) we explicitly apply morphological K-corrections; (ii) we measure asymmetries in galaxies artificially redshifted to z(d) = 1.0 to deal with loss of morphological information with redshift; and (iii) we take into account the observational errors in z and A, which tend to overestimate the merger fraction, though use of maximum likelihood techniques. Results. We obtain morphological merger fractions (f(m)(mph)) below 0.06 up to z similar to 1. Parameterizing the merger fraction evolution with redshift as f(m)(mph) (z) = f(m)(mph)(0)(1 + z)(m), we find that m = 1.8 +/- 0.5 for M-B <= -20 galaxies, while m = 5.4 +/- 0.4 for M-star >= 10(10) M-circle dot galaxies. When we translate our merger fractions to merger rates (R-m(mph)), their evolution, parameterized as R-m(mph) (z) = R-m(mph) (0)(1+ z)(n), is quite similar in both cases: n = 3.3 +/- 0.8 for M-B <= -20 galaxies, and n = 3.5 +/- 0.4 for M-star >= 10(10) M-circle dot galaxies. Conclusions. Our results imply that only similar to 8% of today's M-star >= 10(10) M circle dot galaxies have undergone a disc-disc major merger since z similar to 1. In addition, similar to 21% of M-star >= 10(10) M-circle dot galaxies at z similar to 1 have undergone one of these mergers since z similar to 1.5. This suggests that disc-disc major mergers are not the dominant process in the evolution of M-star >= 10(10) M-circle dot galaxies since z similar to 1, with only 0.2 disc-disc major mergers per galaxy, but may be an important process at z > 1, with similar to 1 merger per galaxy at 1 < z < 3.