Observational Constraints on Interacting Dark Matter Model Without Dark Energy

The interacting dark matter (IDM) scenario allows for the acceleration of the Universe without Dark Energy. We constrain the IDM model by using the newly revised observational data including $H(z)$ data and Union2 SNe Ia via the Markov chain Monte Carlo method. When mimicking the $\Lambda$CDM model, we obtain a more stringent upper limit to the effective annihilation term at $\kappa C_1\approx 10^{-3.4}\rm{Gyr}^{-1}$, and a tighter lower limit to the relevant mass of Dark Matter particles at $M_x\approx 10^{-8.6}\rm{Gev}$. When mimicking the $w$CDM model, we find that the effective equation of state of IDM is consistent with the concordance $\Lambda$CDM model and appears to be most consistent with the effective phantom model with a constant EoS for which $w<-1$.