The sizes of galaxies are known to be closely related with their masses , luminosities , redshifts and morphologies .
However , when we fix these quantities and morphology , we still find large dispersions in the galaxy size distribution .
We investigate the origin of these dispersions for red early-type galaxies , using two SDSS-based catalogs .
We find that the sizes of faint galaxies ( \log ( M _ { \textrm { \scriptsize dyn } } / M _ { \odot } ) \lower 2.15 pt \hbox { $ \buildrel < % \over { \sim } $ } 10.3 or ^ { 0.1 } M _ { r } \lower 2.15 pt \hbox { $ \buildrel > \over { \sim } $ } -19.5 , where ^ { 0.1 } M _ { r } is the r -band absolute magnitude , k-corrected to z = 0.1 ) are affected more significantly by luminosity , while the sizes of bright galaxies ( \log ( M _ { \textrm { \scriptsize dyn } } / M _ { \odot } ) \lower 2.15 pt \hbox { $ \buildrel > % \over { \sim } $ } 11.4 or ^ { 0.1 } M _ { r } \lower 2.15 pt \hbox { $ \buildrel < \over { \sim } $ } -21.4 ) are by dynamical mass . At fixed mass and luminosity , the sizes of low-mass galaxies ( \log ( M _ { \textrm { \scriptsize dyn } } / M _ { \odot } ) \sim 10.45 and ^ { 0.1 } M _ { r } \sim - 19.8 ) are relatively less sensitive to their colors , color gradients and axis ratios .
On the other hand , the sizes of intermediate-mass ( \log ( M _ { \textrm { \scriptsize dyn } } / M _ { \odot } ) \sim 10.85 and ^ { 0.1 } M _ { r } \sim - 20.4 ) and high-mass ( \log ( M _ { \textrm { \scriptsize dyn } } / M _ { \odot } ) \sim 11.25 and ^ { 0.1 } M _ { r } \sim - 21.0 ) galaxies significantly depend on those parameters , in the sense that larger red early-type galaxies have bluer colors , more negative color gradients ( bluer outskirts ) and smaller axis ratios .
These results indicate that the sizes of intermediate- and high-mass red early-type galaxies are significantly affected by their recent minor mergers or rotations , whereas the sizes of low-mass red early-type galaxies are affected by some other mechanisms .
Major dry mergers also seem to have influenced on the size growth of high-mass red early-type galaxies .