  During the jamming of thermal colloids, the first peak of the pair
distribution function shows a maximum height $g_1^{\rm max}$. We find that
$g_1^{\rm max}$ is accompanied by significant change of material properties and
thus signifies the transition from unjammed to jammed glasses. The scaling laws
at $g_1^{\rm max}$ lead to scaling collapse of structural and thermodynamic
quantities, indicating the criticality of the T=0 jamming transition. The
physical significance of $g_1^{\rm max}$ is highlighted by its coincidence with
the equality of the kinetic and potential energy and the maximum fluctuation of
the coordination number. In jammed glasses, we find the strong coupling between
the isostaticity and flattening of the density of vibrational states at the
isostatic temperature scaled well with the compression.
