Using high-resolution HST/Wide Field Camera 3 F125W imaging from the CANDELS-COSMOS field , we report the the structural and morphological properties of Extremely Red Objects ( EROs ) at z \sim 1 .
Based on the UVJ color criteria , we separate EROs into two types : old passive galaxies ( OGs ) and dusty star-forming galaxies ( DGs ) .
For a given stellar mass , we find that the mean size of OGs ( DGs ) is smaller by a factor of \sim 2 ( 1.5 ) than that of present-day early-type ( late-type ) galaxies at rest-frame optical wavelength .
We derive the average effective radii of OGs and DGs , corresponding to 2.09 \pm 1.13 kpc and 3.27 \pm 1.14 kpc , respectively .
Generally , The DGs are heterogeneous , with mixed features including bulges , disks , and irregular structures , with relatively high M _ { 20 } , small size and low G , while OGs are elliptical-like compact morphologies with lower M _ { 20 } , larger size and higher G , indicating the more concentrated and symmetric spatial extent of stellar population distribution in OGs than DGs .
The findings imply that OGs and DGs have different evolutionary processes , and the minor merger scenario is the most likely mechanism for the structural properties of OGs .
However , the size evolution of DGs is possibly due to the secular evolution of galaxies .