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