GEMS: Galaxy fitting catalogues and testing parametric galaxy fitting codes

Understand

In the context of measuring structure and morphology of intermediate redshift galaxies with recent HST/ACS surveys, we tune, test, and compare two widely used fitting codes (GALFIT and GIM2D) for fitting single-component Sersic models to the light profiles of both simulated and real galaxy data.

• We find that fitting accuracy depends sensitively on galaxy profile shape.
• Exponential disks are well fit with Sersic models and have small measurement errors, whereas fits to de Vaucouleurs profiles show larger uncertainties owing to the large amount of light at large radii.
• We find that both codes provide reliable fits and little systematic error, when the effective surface brightness is above that of the sky.