Morphological and photometric properties of active and non-active galaxies in the green valley

Abstract

Context: The differences in properties of active and non-active galaxies in the green valley have been studied in the quest of finding the driving mechanism behind the evolutionary transition from the blue cloud to the red sequence galaxies.Aims: Using COSMOS data, as one of the deepest surveys, and X-ray detected active galaxies, we studied their properties in the green valley, and established the differences in comparison with the non-active ones.Methods: Green valley galaxies were selected using the U-B colour criteria of 0.8 ≤ U- B ≤ 1.2. We then studied different properties between the two samples such as their morphologies, colours, stellar masses, photometric redshift distributions, and sizes, and performed a statistical comparative study.Results: We found that in the green valley, active galaxies are dominated by earlier morphological types (elliptical and lenticular galaxies), are more massive, have higher photometric redshifts and redder colours than non-active galaxies.Conclusions: Our findings suggest that the non-active galaxies in the green valley are different from the active ones, with active galaxies being more evolved.Keywords: galaxies: active, galaxies: fundamental parameters, galaxies: structure, Xrays: galaxies