Constraints on barotropic dark energy models by a new phenomenological q ( z ) parameterization

In this paper, we propose a new phenomenological two parameter parameterization of q ( z ) to constrain barotropic dark energy models by considering a spatially flat Universe, neglecting the radiation component, and reconstructing the effective equation of state (EoS). This two free-parameter EoS reconstruction shows a non-monotonic behavior, pointing to a more general fitting for the scalar field models, like thawing and freezing models. We constrain the q ( z ) free parameters using the observational data of the Hubble parameter obtained from cosmic chronometers, the joint-light-analysis Type Ia Supernovae (SNIa) sample, the Pantheon (SNIa) sample, and a joint analysis from these data. We obtain, for the joint analysis with the Pantheon (SNIa) sample a value of q ( z ) today, q_0=-0.51[ +0.09; -0.10 ] , and a transition redshift, z_t=0.65[ +0.19; -0.17 ] (when the Universe change from an decelerated phase to an accelerated one). The effective EoS reconstruction and the ω ' – ω plane analysis point towards a transition over the phantom divide, i.e. ω =-1 , which is consistent with a non parametric EoS reconstruction reported by other authors.