Massive galaxies at higher redshifts ( z > 2 ) show different characteristics from their local counterparts : They are compact and most likely have a disk .
In this study , we trace the evolution of local massive galaxies by performing a detailed morphological analysis , namely , fitting single Sérsic profiles and performing bulge+disk decompositions .
We analyze \sim 250 massive galaxies selected from all CANDELS fields ( COSMOS , UDS , EGS , GOODS-South and GOODS-North ) .
We confirm that both star-forming and quiescent galaxies increase their sizes significantly from z \approx 2.5 to the present day .
The global Sérsic index of quiescent galaxies increases over time ( from n \approx 2.5 to n > 4 ) , while that of star-forming galaxies remains roughly constant ( n \approx 2.5 ) .
By decomposing galaxy profiles into bulge+disk components , we find that massive galaxies at high redshift have prominent stellar disks , which are also evident from visual inspection of the images .
By z \approx 0.5 , the majority of the disks disappear and massive quiescent galaxies begin to resemble the local elliptical galaxies .
Star-forming galaxies have lower bulge-to-total ratios ( B / T ) than their quiescent counterparts at each redshift bin .
The bulges of star-forming and quiescent galaxies follow different evolutionary histories , while their disks evolve similarly .
Based on our morphological analysis and previous cosmological simulations , we argue that major mergers , along with minor mergers , have played a crucial role in the significant size increase of high- z galaxies and the destruction of their massive and large-scale disks .