Is the dark matter warm or cold? That would be determined by the cosmic observations. In this paper, we loose the constraint to zero $w_{dm}$ and assume a constant equation of state (EoS) of dark matter. By using the currently available cosmic observations which include type-Ia supernovae (SN), baryon acoustic oscillation (BAO) and cosmic microwave background radiation (CMB) from the firs release of {\it Planck} through the Markov Chain Monte Carlo method, we found the EoS of dark matter in $3\sigma$ regions: $w_{dm}=0.00118_{-0.000817-0.00162-0.00212}^{+0.000823+0.00161+0.00211}$. It implies a little warm dark matter is favored up to $1\sigma$ region.
Date added: Tue, 8 Oct 13