Constraining a New Type of Dark Energy Model from Present Observations

We propose a new type of dark energy (DE) model, in which the equation of state of DE ωde is a simple function of the fractional energy density Ωde instead of the redshift z. We assume three DE models of this type, and fit them with present observations to get constraints of DE, which are also compared with the CPL model. It is shown that a suitable ωde(Ωde) model can give smaller χ2 or smaller errors of ωde than that of the CPL model. This new type of DE model can help to study the essential properties and nature of DE. (geophysics, astronomy, and astrophysics)