A high stellar velocity dispersion for a compact massive galaxy at z=2.2

Understand

Recent studies have found that the oldest and most luminous galaxies in the early Universe are surprisingly compact, having stellar masses similar to present-day elliptical galaxies but much smaller sizes.

• This finding has attracted considerable attention as it suggests that massive galaxies have grown by a factor of ~five in size over the past ten billion years.
• A key test of these results is a determination of the stellar kinematics of one of the compact galaxies: if the sizes of these objects are as extreme as has been claimed, their stars are expected to have much higher velocities than those in present-day galaxies of the same mass.
• Here we report a measurement of the stellar velocity dispersion of a massive compact galaxy at redshift z=2.186, corresponding to a look-back time of 10.7 billion years.