The Asymmetry of the Nearby Galaxies in GALEX UV & H{alpha } Images
Résumé
In order to quantitatively classify galaxies and to study the relationship between the spatial distribution of the light in galaxies and their physical properties, we are investigating the multi-wavelength rotational asymmetry (parameterized by asymmetry index A) in a sample of several hundred nearby galaxies. As part of this effort we have calculated asymmetry indices for 305 galaxies selected from the GALEX (Galaxy Evolution Explorer) Nearby Galaxies Survey and Medium-deep Imaging Survey, and for 71 spiral galaxies obtained from the Carnegie Halpha imaging survey. After a careful determination of the centers of the galaxies we have computed the asymmetry both global and as a function of the galactic radius. The main objective of this project is to classify the radial asymmetry profiles and to investigate their relationship with the galaxies' morphological type and physical properties (luminosity, mass, environment, etc.). In particular, the asymmetry of spiral galaxies may provide useful information about the distribution of star forming regions in the galactic disks. We find that the asymmetry number increases as the (FUV-NUV) color of galaxies increases and also as morphological type changes from elliptical to irregular. We are in the process of adding asymmetry numbers measured in the light of H{alpha } band. We also plan to investigate the influence of other structural properties such as the concentration of light (C) and the Gini coefficient. First results will be included in the GALEX Atlas of Nearby Galaxies.