Recovering the Tidal Field in the Projected Galaxy Distribution
  We present a method to recover and study the projected gravitational tidal
forces from a galaxy survey containing little or no redshift information. The
method and the physical interpretation of the recovered tidal maps as a tracer
of the cosmic web are described in detail. We first apply the method to a
simulated galaxy survey and study the accuracy with which the cosmic web can be
recovered in the presence of different observational effects, showing that the
projected tidal field can be estimated with reasonable precision over large
regions of the sky. We then apply our method to the 2MASS survey and present a
publicly available full-sky map of the projected tidal forces in the local
Universe. As an example of an application of these data we further study the
distribution of galaxy luminosities across the different elements of the cosmic
web, finding that, while more luminous objects are found preferentially in the
most dense environments, there is no further segregation by tidal environment.
