In this work , we consider the cosmological constraints on the holographic Ricci dark energy proposed by Gao et al . [ Phys .
Rev .
D 79 , 043511 ( 2009 ) ] , by using the observational data currently available .
The main characteristic of holographic Ricci dark energy is governed by a positive numerical parameter \alpha in the model .
When \alpha < 1 / 2 , the holographic Ricci dark energy will exhibit a quintomlike behavior ; i.e. , its equation of state will evolve across the cosmological-constant boundary w = -1 .
The parameter \alpha can be determined only by observations .
Thus , in order to characterize the evolving feature of dark energy and to predict the fate of the universe , it is of extraordinary importance to constrain the parameter \alpha by using the observational data .
In this paper , we derive constraints on the holographic Ricci dark energy model from the latest observational data including the Union sample of 307 type Ia supernovae , the shift parameter of the cosmic microwave background given by the five-year Wilkinson Microwave Anisotropy Probe observations , and the baryon acoustic oscillation measurement from the Sloan Digital Sky Survey .
The joint analysis gives the best-fit results ( with 1 \sigma uncertainty ) : \alpha = 0.359 ^ { +0.024 } _ { -0.025 } and \Omega _ { m 0 } = 0.318 ^ { +0.026 } _ { -0.024 } .
That is to say , according to the observations , the holographic Ricci dark energy takes on the quintom feature .
Finally , in light of the results of the cosmological constraints , we discuss the issue of the scalar-field dark energy reconstruction , based on the scenario of the holographic Ricci vacuum energy .