Volume 516, June-July 2010
|Number of page(s)||4|
|Section||Cosmology (including clusters of galaxies)|
|Published online||21 July 2010|
The Hubble diagram for a system within dark energy: the location of the zero-gravity radius and the global Hubble rate
Tuorla Observatory, Department of Physics and Astronomy, University of Turku, 21500 Piikkiö, Finland e-mail: firstname.lastname@example.org
2 Sternberg Astronomical Institute, Moscow University, Moscow 119899, Russia
Accepted: 18 April 2010
Aims. Here we continue to discuss the principle of the local measurement of dark energy using the normalized Hubble diagram describing the environment of a system of galaxies.
Methods. We calculate the present locus of test particles injected a fixed time ago (~the age of the universe), in the standard Λ cosmology and for different values of the system parameters (the model includes a central point mass M and a local dark energy density ρloc) and discuss the position of the zero-gravity distance Rv in the Hubble diagram.
Results. Our main conclusion are: 1) when the local DE density ρloc is equal to the global DE density ρv, the outflow reaches the global Hubble rate at the distance R2 = (1+zv)Rv, where zv is the global zero-acceleration redshift (≈0.7 for the standard model). This is also the radius of the ideal Einstein-Straus vacuole, 2) for a wide range of the local-to-global dark energy ratio ρloc/ρv, the local flow reaches the known global rate (the Hubble constant) at a distance R2 1.5 × Rv. Hence, Rv will be between R2/2 and R2, giving upper and lower limits to ρloc/M. For the Local Group, this supports the view that the local density is near the global one.
Key words: Local Group / dark energy / cosmological parameters
© ESO, 2010
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.