Issue |
A&A
Volume 423, Number 2, August IV 2004
|
|
---|---|---|
Page(s) | 421 - 426 | |
Section | Cosmology (including clusters of galaxies) | |
DOI | https://doi.org/10.1051/0004-6361:20040236 | |
Published online | 06 August 2004 |
Generalized Chaplygin gas as a unified scenario of dark matter/energy: Observational constraints
Department of Astronomy, Beijing Normal University, Beijing 100875, PR China e-mail: zong-hong.zhu@nao.ac.jp National Astronomical Observatories, Chinese Academie of Sciences, Beijing 100012, PR China
National Astronomical Observatory, 2-21-1, Osawa, Mitaka, Tokyo 181-8588, Japan
Received:
10
February
2004
Accepted:
30
March
2004
Although various cosmological observations congruously suggest that
our universe is dominated by two dark components, the cold dark matter
without pressure and the dark energy with negative pressure, the nature
and origin of these components is yet unknow.
The generalized Chaplygin gas (gCg), parametrized by an equation of state,
, was recently proposed to be a candidate
of the unified dark matter/energy (UDME) scenarios.
In this work, we investigate some observational constraints on it.
We mainly focus our attention on the constraints from recent measurements of
the X-ray gas mass fractions in clusters of galaxies published by
Allen et al. ([CITE], MNRAS, 334, L11;
[CITE], 342, 257)
and the dimensionless coordinate distances to type Ia supernovae and
Fanaroff-Riley type IIb radio galaxies compiled by
Daly & Djorgovski ([CITE], ApJ, 597, 9).
We obtain the confidence region on the two parameters fully characterizing gCg,
and α, from
a combined analysis of these databases, where
is the
energy density of gCg at present.
It is found that
and
,
at a 95% confidence level,
which is consistent within the errors with the standard dark matter + dark
energy model, i.e., the case of
.
Particularly, the standard Chaplygin gas (
) is ruled out as a
feasible UDME by the data at a 99% confidence level.
Key words: cosmology: cosmological parameters / cosmology: theory / stars: supernovae: general / galaxies: distances and redshifts / X-rays: galaxies: clusters
© ESO, 2004
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