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

Abstract

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 ($r_{\perp }=0.01$ Mpc/h) than previous work. The measured PVD at projected separations $r_{\perp }<1$ Mpc/h increases near-monotonically with increasing luminosity from $\ddot{I}ƒ\approx 200$ km/s at $M_r=-17$ mag to $\ddot{I}ƒ\approx 600$ km/s at $M_r\approx -22$ mag. Analysis of the Gonzalez-Perez (2014) GALFORM semi-analytic model yields no such trend of PVD with luminosity: the model over-predicts the PVD for faint galaxies. This is most likely a result of the model placing too many low-luminosity galaxies in massive halos.

Accepted for publication in MNRAS, 17 pages