Gravitational waves from extragalactic inspiraling binaries: Selection effects and expected detection rates

We examine the selection effects that determine how the population of inspiraling binary compact objects (BCOs) is reflected by those potentially observed with ground-based interferometers like LIGO. We lay the groundwork for the interpretation of future observations in terms of constraints on the real population and, correspondingly, binary star evolution models. To determine the extragalactic population of inspiraling binaries, we combine data on distance and blue luminosity from galaxy catalogs with current models of the Galactic BCO mass distribution to simulate the physical distribution of binaries in the nearby universe. We use Monte Carlo methods to determine the fraction of binaries observable by the LIGO detectors from each galaxy as a function of the BCO chirp mass. We examine separately the role of source distance, sky position, time of detection, and binary system chirp mass on the detection efficiency and selection effects relevant to the three LIGO detectors. Finally, we discuss the implications of the nearby geography of space on anticipated gravitational wave detection and compare our results to those of previous studies, which have assumed uniform galaxy volume density and fixed chirp mass for BCOs. From these considerations, actual BCO inspiral observations or significant upper limits on the coalescence rate anticipated in the near future by ground-based interferometers can be used to improve our knowledge of the Galactic binary inspiral rate and to constrain models of radio pulsar characteristics and binary star evolution channels leading to neutron star or black hole binaries.