Speaker
Description
The presence of Active Galactic Nuclei (AGN) can significantly influence the morphological classification of galaxies, particularly at intermediate and high redshifts where observational limitations further complicate structural measurements. This study investigates how different levels of AGN contribution affect six widely used non-parametric morphological parameters under COSMOS-like conditions down to redshift z ≈ 2. We use a sample of more than 2000 local, non-active galaxies with reliable visual morphological classifications. To simulate the presence of an AGN, we add an unresolved central point source contributing between 5% and 75% of the total galaxy flux. The galaxies are then artificially shifted to fainter magnitudes to reproduce the observational depth, resolution, and noise typical of the COSMOS field. For each simulated image, we remeasure the morphological parameters and assess how they deviate from their original values. Our results show that the combined effect of increasing redshift, decreasing magnitude, and AGN contribution has the strongest impact on galaxy morphology, with spiral galaxies being noticeably more affected than early-type systems. All concentration-based parameters exhibit substantial changes when the AGN contributes more than 25% of the total flux and when galaxies appear fainter than magnitude 23. Among all parameters, the GINI coefficient proves to be the most stable against both AGN contamination and redshift degradation, followed by the moment of light (M20), the Conselice–Bershady concentration index (CCON), and finally the Abraham concentration index (CABR), which is the most sensitive. When using morphological parameters to classify high-redshift active galaxies, we find that a combination of CABR, CCON, and asymmetry provides the best discrimination between morphological types. A secondary but still effective combination is CABR with the GINI coefficient. These results provide insights into the reliability of morphological diagnostics in AGN host galaxies and offer guidance for future morphological studies in deep extragalactic surveys.
| Stream | Science or Engineering |
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