Program: GN-2012A-Q-46

Recent studies have found that massive galaxies in the early Universe are very compact, containing stellar masses similar to present-day elliptical galaxies, but surprisingly have much smaller sizes. This finding has attracted considerable attention, as it suggests that massive galaxies have grown in size by a factor of about five over the past ten billion years (10 Gyr). The exact physical mechanism that allows for the extraordinary growth in size of these objects is unknown. All present proposed scenarios require determining the stellar kinematics of these compact galaxies as the key test to select between different alternatives. So far, despite the extraordinary efforts to obtain these measures, there is not yet a reliable measure of the velocity dispersion of a single compact massive high-z galaxy. We propose to address this issue and put a stringent constraint on massive galaxies assembly scenarios by obtaining the first solid measurement of distant compact galaxies velocity dispersions (S/N~10) at z~1.8 using Gemini+NIFS+Altair.