We present Keck-I MOSFIRE near-infrared spectroscopy for a sample of 13 compact star-forming galaxies (SFGs) at redshift $2\leq z \leq2.5$ with star formation rates of SFR$\sim$100M$_{ \odot}$ y$^{ -1}$ and masses of log(M/M$_{ \odot}$)$\sim10.8$. Their high integrated gas velocity dispersions of $\sigma_{ \rm{ int}}$=230$^{ +40}_{ -30}$ km s$^{ -1}$, as measured from emission lines of H$_{ \alpha}$ and [OIII], and the resultant M$_{ \star}-\sigma_{ \rm{ int}}$ relation and M$_{ \star}$$-$M$_{ \rm{ dyn}}$ all match well to those of compact quiescent galaxies at $z\sim2$, as measured from stellar absorption lines. Since log(M$_{ \star}$/M$_{ \rm{ dyn}}$)$=-0.06\pm0.2$ dex, these compact SFGs appear to be dynamically relaxed and more evolved, i.e., more depleted in gas and dark matter ($<$13$^{ +17}_{ -13}$\%) than their non-compact SFG counterparts at the same epoch. Without infusion of external gas, depletion timescales are short, less than $\sim$300 Myr. This discovery adds another link to our new dynamical chain of evidence that compact SFGs at $z\gtrsim2$ are already losing gas to become the immediate progenitors of compact quiescent galaxies by $z\sim2$.
Categories: astro-ph.GA