SIMULATING OUR COSMOLOGICAL NEIGHBORHOOD - MOCK CATALOGS FOR VELOCITYANALYSIS

We describe the construction of an N-body simulation that mimics the t rue velocity and mass-density fields in a box of side 256 h(-1) Mpc ab out the Local Group, and the production of mock catalogs that mimic in detail current catalogs of redshifts and peculiar velocities. Our mai n purpose is to provide a tool for developing and testing reconstructi on methods, but the different components of the method can be used on their own in other applications. The initial conditions in the present application are based on the IRAS 1.2 Jy redshift survey, assuming th at galaxies trace mass and Omega = 1. A density field smoothed with a Gaussian of radius 5 h(-1) Mpc is recovered from the redshift survey, using quasi-linear theory and a power-preserving filter. The correspon ding potential field is traced back to the linear regime using the Zel dovich-Bernoulli equation. Small-scale power is added by means of cons trained realization to mimic fluctuations on galactic scales. The grav itating system is evolved forward in time with a particle-mesh code of 2 h(-1) Mpc resolution and stopped when sigma(g) = 0.7. The result re produces the real dynamical structures on large scales and the statist ical properties of the structure down to galactic scales. ''Galaxies'' are identified via a linear biasing scheme (b = 1.35), and they are d ivided into ''spirals'' and ''ellipticals'' to obey Dressier's morphol ogy-density relation. The galaxies are assigned internal velocity para meters (eta) and absolute magnitudes scattered about an assumed mean T ully-Fisher relation. They are then ''observed'' as magnitude-limited samples, trying to mimic the selection criteria of the data sets const ituting the Mark III catalog of peculiar velocities. Artifical IRAS 1. 2 Jy redshift surveys are also compiled. The simulations and mock cata logs will be made available electronically as benchmarks for testing r econstruction methods.