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

astro-ph.CO

/ Authors

J. Loveday, L. Christodoulou, P. Norberg, J. A. Peacock, I. K. Baldry, J. Bland-Hawthorn, M. J. I. Brown, M. Colless, S. P. Driver, B. W. Holwerda

and 5 more authors

A. M. Hopkins, P. R. Kafle, J. Liske, A. R. Lopez-Sanchez, E. N. Taylor

/ 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 ($r_\bot = 0.01$ Mpc/h) than previous work. The measured PVD at projected separations $r_\bot <~ 1$ Mpc/h increases near-monotonically with increasing luminosity from $σ\approx 200$ km/s at $M_r = -17$ mag to $σ\approx 600$ 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.