Mathematics – Logic
Scientific paper
Jan 2010
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2010aas...21540805b&link_type=abstract
American Astronomical Society, AAS Meeting #215, #408.05; Bulletin of the American Astronomical Society, Vol. 42, p.232
Mathematics
Logic
Scientific paper
Dark energy was first detected at large Gpc distances. If it is indeed vacuum energy formulated as Einstein's cosmological constant, Λ, dark energy should have dynamical effects at much smaller scales. Here we discuss its measurement on Mpc scales of galaxy groups, in particular our Local Group (LG). We use HST estimates of distances and motions of LG members and Hubble outflow neighbors along with the age of the universe. We estimate simultaneously and in a self-consistent way the local density of dark energy and the gravitating mass within the LG. The lower and upper dark energy density estimates are mainly determined by the observational maximum and minimum (1.2 - 1.6 Mpc) of the zero-gravity radius between internal group motions and the neighboring Hubble outflow. The local dark energy density is observationally constrained to be 0.8 to 3.7 times the globally measured dark energy density of 7x10-30 g/cm3. The agreement between this independently determined range and the global value on scales differing by a factor of 1000 is new strong support for universal dark energy as described by Λ. For our dark energy range, the LG mass is 3.1 to 5.8x1012 Solar masses. These mass limits are mainly determined by the age of the universe, the binding condition for the Local Group M31-Milky Way binary as well as the observationally determined zero-gravity radii range. Accepting the globally determined dark energy density, the dark (and baryonic) mass range is narrowed to 3.3 - 3.8 x 1012 Solar masses. The best fit to the neighbors’ Hubble outflow is obtained with the upper limit to the mass. For other galaxy group mass estimates, one should take into account the dark energy, including it in the virial theorem.
Byrd Gene Gilbert
Chernin Arthur D.
Dolgachev V. P.
Domozhilova L. M.
Teerikorpi Pekka
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