Age constraints on the cosmic equation of state

Free access article

Issue		A&A Volume 467, Number 2, May IV 2007


Page(s)		421 - 426
Section		Cosmology (including clusters of galaxies)
DOI		http://dx.doi.org/10.1051/0004-6361:20066632

A&A 467, 421-426 (2007)
DOI: 10.1051/0004-6361:20066632

Age constraints on the cosmic equation of state

M. A. Dantas¹, J. S. Alcaniz¹, D. Jain², and A. Dev³

¹ Observatório Nacional, Rua Gal. José Cristino 77, 20921-400 Rio de Janeiro, RJ, Brasil
e-mail: [aldinez;alcaniz]@on.br
² Deen Dayal Updhyaya College, University of Delhi, Delhi 110 015, India
e-mail: deepak@physics.du.ac.in
³ Miranda House, University of Delhi, Delhi 110007, India

(Received 24 October 2006 / Accepted 9 January 2007 )

Abstract
Dark energy is the invisible fuel that seems to drive the current acceleration of the Universe. Its presence, which is inferred from an impressive convergence of high-quality observational results along with some sucessful theoretical predictions, is also supported by the current estimates of the age of the Universe from dating of local and high-z objects. In this work we study observational constraints on the dark energy equation of state (w) from lookback time measurements of high-z galaxies, as recently published by the Gemini Deep Deep Survey (GDDS). To build up our lookback time sample from these observations we use 8 high-z galaxies in the redshift interval $1.3 \leq z \leq 2.2$ and assume the total expanding age of the Universe to be $t_{0}^{\rm obs} = 13.6^{+0.4}_{-0.3}$ Gyr, as obtained from current cosmic microwave background data. We show that these age measurements are compatible with values of w close to -1, although there is still space for quintessence (w > -1) and phantom (w < -1) behaviors. To break possible degeneracies in the $\Omega_{\rm {m}} - w$ plane, we also discuss the bounds on this parametric space when GDDS lookback time measurements are combined with the most recent SNe Ia, CMB, and LSS data.

Key words: cosmology: theory -- cosmological parameters -- distance scale

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