Galaxy and Mass Assembly (GAMA): small-scale anisotropic galaxy clustering and the pairwise velocity dispersion of galaxies

The galaxy pairwise velocity dispersion (PVD) can provide important tests of non-standard gravity and galaxy formation models. We describe measurements of the PVD of galaxies in the Galaxy and Mass Assembly (GAMA) survey as a function of projected separation and galaxy luminosity. Due to the faint magnitude limit (r < 19.8) and highly complete spectroscopic sampling of the GAMA survey, we are able to reliably measure the PVD to smaller scales (r_⊥ = 0.01 h ^{- 1} Mpc) than previous work. The measured PVD at projected separations r_⊥ ≲ 1 h ^{- 1} Mpc increases near monotonically with increasing luminosity from σ₁₂ ≈ 200 km s ^{- 1} at M_r = -17 mag to σ₁₂ ≈ 600 km s ^{- 1} at M_r ≈ -22 mag. Analysis of the Gonzalez-Perez et al. (2014) GALFORM semi-analytic model yields no such trend of PVD with luminosity: the model overpredicts the PVD for faint galaxies. This is most likely a result of the model placing too many low-luminosity galaxies in massive haloes.