  The transverse momentum ($p_{\rm T}$) and centrality dependence of the
azimuthal anisotropy ($v_{2}$) are measured for charged hadrons in different
energies and collision species by the PHENIX experiment at RHIC. We find that
$v_{2}$ divided by the participant eccentricity of the initial geometry
proportionally increases with the number of participants to the 1/3 power
except at small $N_{\rm part}$ in Cu+Cu at $\sqrt{s_{\rm NN}}$ = 62.4 GeV.
Taking the eccentricity and quark number scaling into account, there is a
universal scaling for $v_{2}$ with different energies and collision sizes. The
results indicate that $v_{2}$ is determined by more than just the geometrical
eccentricity. It also depends on the size of collision. We also report that
both the behaviors of $v_{2}$ and $p_{\rm T}$ distributions can be understood
from the thermal nature of produced particles based on hydro-dynamical
behavior.
