DETERMINATION OF MALMQUIST BIAS AND SELECTION EFFECTS FROM MONTE-CARLO SIMULATIONS

Maps of the peculiar velocity field derived from distance relations ar e affected by Malmquist type bias and selection effects. Because of th e large number of interdependent effects, they are in most cases diffi cult to treat analytically. Monte Carlo simulations are used to unders tand and evaluate these effects. In these simulations the ''true'' spa tial distribution and relevant properties of galaxies as well as selec tion effects and observational uncertainties are realistically modeled . The results of the simulation can be directly applied to correct obs erved peculiar velocity maps. The simulation is used to investigate bi ases in samples of measured peculiar velocities by Lynden-Bell et al. (ApJ, 326, 19, 1988). Willick (ApJ, 351, L5, 1990) and the new sample of spiral galaxies by Haynes ct al. (BAAS, 25, 1403, 1993). Based on t he results obtained from the application of our method to toy models w e find that the method is a useful tool to estimate the bias induced b oth by inhomogeneities and selection effects. This is a crucial step f or the analysis of-the Haynes ct al. sample which was selected with a redshift dependent criterion. (C) 1995 American Astronomical Society.