Dünner, RReisenegger, AMeza, AAraya, PAQuintana, H2024-07-062024-07-062007-04-21MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Volume 376, Issue 4, Page 1577-15870035-8711https://repositorio.unab.cl/handle/ria/58248INDEXACIÓN: WEB OF SCIENCE.An exponentially expanding Universe, possibly governed by a cosmological constant, forces gravitationally bound structures to become more and more isolated, eventually becoming causally disconnected from each other and forming so-called 'island universes'. This new scenario reformulates the question about which will be the largest structures that will remain gravitationally bound, together with requiring a systematic tool that can be used to recognize the limits and mass of these structures from observational data, namely redshift surveys of galaxies. Here we present a method, based on the spherical collapse model and N-body simulations, by which we can estimate the limits of bound structures as observed in redshift space. The method is based on a theoretical criterion presented in a previous paper that determines the mean density contrast that a spherical shell must have in order to be marginally bound to the massive structure within it. Understanding the kinematics of the system, we translated the real-space limiting conditions of this 'critical' shell to redshift space, producing a projected velocity envelope that only depends on the density profile of the structure. From it we created a redshift-space version of the density contrast that we called 'density estimator', which can be calibrated from N-body simulations for a reasonable projected velocity envelope template, and used to estimate the limits and mass of a structure only from its redshift-space coordinates.enmethods : N-body simulationsgalaxies : clusters : generalgalaxies : kinematics and dynamicslarge-scale structure of UniverseArtículo10.1111/j.1365-2966.2007.11550.x