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Determining the equation of state of dark energy from angular size of compact radio sources and X-ray gas mass fraction of galaxy clusters

Zong-Hong Zhu·Masa-Katsu Fujimoto·Xiang-Tao He
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Abstract

Using recent measurements of angular size of high-z milliarcsecond compact radio sources compiled by Gurvits, Kellermann and Frey (1999) and X-ray gas mass fraction of galaxy clusters published by Allen et al. (2002,2003), we explore their bounds on the equation of state, omega_x = p_x/rho_x, of the dark energy, whose existence has been congruously suggested by various cosmological observations. We relaxe the usual constraint omega_x >= -1, and find that combining the two databases yields a nontrivial lower bound on omega_x. Under the assumption of a flat universe, we obtain a bound -2.22 < omega_x < -0.62 at 95.4% confidence level. The 95.4% confidence bound goes to -1 =< omega_x < -0.60 when the constraint omega_x >= -1 is imposed.

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Zong-Hong Zhu, Masa-Katsu Fujimoto, Xiang-Tao He. 2004-01-08. Determining the equation of state of dark energy from angular size of compact radio sources and X-ray gas mass fraction of galaxy clusters. https://doi.org/10.1051/0004-6361%3A20034327

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