Issue |
A&A
Volume 507, Number 3, December I 2009
|
|
---|---|---|
Page(s) | 1271 - 1276 | |
Section | Cosmology (including clusters of galaxies) | |
DOI | https://doi.org/10.1051/0004-6361/200912762 | |
Published online | 01 October 2009 |
Local dark matter and dark energy as estimated on a scale of ~1 Mpc in a self-consistent way
1
Tuorla Observatory, Department of Physics and Astronomy, University of Turku, 21500 Piikkiö, Finland e-mail: pekkatee@utu.fi
2
Sternberg Astronomical Institute, Moscow University, Moscow 119899, Russia
3
University of Alabama, Tuscaloosa, AL 35487-0324, USA
Received:
24
June
2009
Accepted:
14
September
2009
Context. Dark energy was first detected from large distances on gigaparsec scales. If it is vacuum energy (or Einstein's Λ), it should also exist in very local space. Here we discuss its measurement on megaparsec scales of the Local Group.
Aims. We combine the modified Kahn-Woltjer method for the Milky Way-M 31 binary and the HST observations of the expansion flow around the Local Group in order to study in a self-consistent way and simultaneously the local density of dark energy and the dark matter mass contained within the Local Group.
Methods. A theoretical model is used that accounts for the dynamical effects of dark energy on a scale of ~1 Mpc.
Results. The local dark energy density is put into the range
0.8-3.7 (
is the globally measured density), and
the Local Group mass lies within 3.1-5.8
1012
.
The lower limit of the local dark energy density,
about 4/5
the global value, is determined by the natural binding condition for the group
binary and the maximal zero-gravity radius. The near
coincidence of two values measured with
independent methods on scales differing by ~1000
times is remarkable. The mass ~4
1012
and
the local dark energy density ~
are also consistent
with the expansion flow close to the Local Group, within the standard
cosmological model.
Conclusions. One should take into account the dark energy in dynamical mass estimation methods for galaxy groups, including the virial theorem. Our analysis gives new strong evidence in favor of Einstein's idea of the universal antigravity described by the cosmological constant.
Key words: galaxies: Local Group / cosmology: dark matter / cosmology: cosmological parameters
© ESO, 2009
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