Alignments of Galaxy Group Shapes with Large Scale Structure
  In this paper we analyse the alignment of galaxy groups with the surrounding
large scale structure traced by spectroscopic galaxies from the Sloan Digital
Sky Survey Data Release 7. We characterise these alignments by means of an
extension of the classical two-point cross-correlation function, developed by
Paz et al. 2008 (arXiv:0804.4477, MNRAS 389 1127). We find a strong alignment
signal between the projected major axis of group shapes and the surrounding
galaxy distribution up to scales of 30 Mpc/h. This observed anisotropy signal
becomes larger as the galaxy group mass increases, in excellent agreement with
the corresponding predicted alignment obtained from mock catalogues and LCDM
cosmological simulations. These measurements provide new direct evidence of the
adequacy of the gravitational instability picture to describe the large-scale
structure formation of our Universe.
