Green valley galaxies as a transition population in different environments

Abstract

We present a comparative analysis of the properties of passive, star-forming and transition (green valley) galaxies, in four discrete environments: field, groups, the outskirts and the core of X-ray clusters. We construct samples of galaxies from the SDSS in these environments so that they are bound to have similar redshift distributions. The classification of galaxies into the three sequences is based on the UV-optical colour NUV−r. We study a number of galaxy properties: stellar mass, morphology, specific star formation rate and the history of star formation. The analysis of green valley galaxies reveals that the physical mechanisms responsible for external quenching become more efficient moving from the field to denser environments. We confirm previous findings that green valley galaxies have intermediate morphologies, moreover, we find that this appears to be independent of the environment. Regarding the stellar mass of green valley galaxies, we find that they tend to be more massive in the field than in denser environments. On average, green valley galaxies account for ∼ 20% of all galaxies in groups and X-ray clusters. We find evidence that the field environment is inefficient in transforming low mass galaxies. Green valley galaxies have average star formation histories intermediate between passive and star forming galaxies, and have a clear and consistent dependence on the environment: both, the quenching time, and the amplitude of the star formation rate, decrease towards higher density environments.

Variation of physical properties across the green valley for local galaxies

“…We combine the morphological classification of Galaxy Zoo (Lintott et al 2011) with the environment catalog (Yang et al 2007) and investigate the effects of environment on the morphologies. Our result shows that the morphology is almost independent of the environment, which is consistent with Coenda et al (2018). Furthermore, the stellar mass of our sample is > 10 10 M ⊙ .…”

Anisotropic infall in the outskirts of OmegaWINGS galaxy clusters

“…Moreover, the CMD correlates with the environment (e.g. Schawinski et al 2007, Cooper et al 2010b, Coenda et al 2018) and morphological types (e.g. Takamiya et al 1995, Schawinski et al 2009, Masters et al 2010.…”

Star formation in low-redshift cluster dwarf galaxies

“…These galaxies may be in the process of being quenched and moving from the blue cloud into the redsequence region (Bremer et al 2018;Belfiore et al 2018). Conversely, some red-sequence galaxies may have recently had their star formation reignited and are transitioning back to the blue cloud (Coenda et al 2018;Darvish et al 2018).…”