Formation of disc galaxies around z~2
  We present combined evolution of morphological and stellar properties of
galaxies on the two sides of z=2 (2.0<z<4.0 and 1.5<z<2.0) in CDFS, with
ground-based spectroscopic redshifts. We perform bulge-disc decomposition on
their images in J and H filters, from the 3DHST Legacy Survey obtained using
HST/WFC3. Combining morphological information with stellar properties, we
provide a detailed account of the formation/growth of discs and spheroids
around z~2. The fraction of 2-component (bulge+disc) systems increases from
~46% for z>2 to ~70% for z<2, compensating for the fall in population of pure
discs and pure spheroids. All quiescent outliers of our full sample on the
main-sequence, are 2-component systems, belonging to the lower redshift range
(z<2). The doubling of stellar mass of 2-component systems and decrease in
their SFR by the same factor, suggests that mechanisms involved in
morphological transformations are also responsible for the quenching of their
star formation activity. Interestingly, while there is substantial increase in
the size (~2.5 times) and mass (~5 times) of pure discs, from z>2 to z<2, pure
spheroids maintain roughly the same values. Additionally, while bulge hosting
discs witness an expansion in scale length (~1.3 times), their bulge sizes as
well as bulge to total light ratio see no evolution, suggesting that z~2 is
pre-dominantly a disc formation period.
