| Issue |
A&A
Volume 417, Number 3, April III 2004
|
|
|---|---|---|
| Page(s) | 833 - 837 | |
| Section | Cosmology (including clusters of galaxies) | |
| DOI | https://doi.org/10.1051/0004-6361:20034327 | |
| Published online | 26 March 2004 | |
Determining the equation of state of dark energy from angular size of compact radio sources and X-ray gas mass fraction of galaxy clusters
1
Department of Astronomy, Beijing Normal University, Beijing 100875, China
2
National Astronomical Observatory, 2-21-1, Osawa, Mitaka, Tokyo 181-8588, Japan e-mail: fujimoto.masa-katsu@nao.ac.jp
Corresponding author: Zong-Hong Zhu, zong-hong.zhu@nao.ac.jp
Received:
15
September
2003
Accepted:
16
December
2003
Using recent measurements of angular size of high-z milliarcsecond
compact radio sources compiled by Gurvits et al. ([CITE]) and
X-ray gas mass fraction of galaxy clusters published by Allen et al.
([CITE], [CITE]), we explore their bounds on the equation of
state, 
, of the dark energy,
whose existence has been congruously suggested by various cosmological
observations.
We relax the usual constraint 
, and find that combining
the two databases yields a nontrivial lower bound on 
.
Under the assumption of a flat universe, we obtain a bound
at 95.4% confidence level.
The 95.4% confidence bound goes to 
when the
constraint is imposed.
Key words: cosmology: cosmological parameters / cosmology: theory / cosmology: distance scale / galaxies: active / radio continuum: galaxies / X-ray: galaxies: clusters
© ESO, 2004
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