Program: GN-2016A-FT-6

In the last decade observations have revealed that galaxies were much more compact at earlier epochs, with quiescent galaxies exhibiting the most extreme differences (factors 4-5 in radius at similar stellar mass). Several mechanisms have been proposed to form these extremely dense galaxies including: (1) compaction via violent disk instabilities or minor merging, (2) gas-rich major mergers, and (3) dissipational collapse formation. Each mechanism would leave characteristic marks on the distribution and motion of stars. However these signatures will disappear with time, age indicators are most sensitive for ~1 Gyr and minor merging will smooth age gradients and diminish rotation. We propose to test these formation models in post-starburst galaxies, which represent the direct, unpolluted products of the quenching process. Although they are extremely rare below z~1, we have leveraged the wide-area of the SDSS spectroscopic survey to identify post-starburst galaxies during the epoch of their decline. Using the GMOS-N IFU spectrograph we propose to measure spatially resolved stellar population and kinematics from stellar absorption features for one of the brightest post-starburst galaxies at z<1. Using these data as a proof of concept we will undertake a statistically significant sample constrain the physical mechanisms responsible for forming compact quiescent galaxies.