A considerable fraction of the massive quiescent galaxies at z \approx 2 , which are known to be much more compact than galaxies of comparable mass today , appear to have a disk .
How well can we measure the bulge and disk properties of these systems ?
We simulate two-component model galaxies in order to systematically quantify the effects of non-homology in structures and the methods employed .
We employ empirical scaling relations to produce realistic-looking local galaxies with a uniform and wide range of bulge-to-total ratios ( B / T ) , and then rescale them to mimic the signal-to-noise ratios and sizes of observed galaxies at z \approx 2 .
This provides the most complete set of simulations to date for which we can examine the robustness of two-component decomposition of compact disk galaxies at different B / T .
We confirm that the size of these massive , compact galaxies can be measured robustly using a single Sérsic fit .
We can measure B / T accurately without imposing any constraints on the light profile shape of the bulge , but , due to the small angular sizes of bulges at high redshift , their detailed properties can only be recovered for galaxies with B / T \mathrel { \hbox { \hbox to 0.0 pt { \hbox { \lower 4.0 pt \hbox { $ \sim$ } } } \hbox { $ > $ } } } 0.2 .
The disk component , by contrast , can be measured with little difficulty .