The galaxy environment in GAMA G3C groups using the Kilo Degree Survey Data Release 3

TL;DR

This study investigates galaxy environments in GAMA G3C groups using KiDS DR3 data, adapting a k-NN method with photometric redshift PDFs to analyze density contrasts and galaxy color gradients, supporting environmental quenching theories.

Contribution

Introduces a modified k-NN technique incorporating photometric redshift PDFs to analyze galaxy environments in G3C groups, validated on simulated data.

Findings

Steeper density contrasts in more massive groups.

Red galaxy fraction gradients are evident across group masses.

Higher density contrast of red galaxies at group centers.

Abstract

We aim to investigate the galaxy environment in GAMA Galaxy Groups Catalogue (G3C) using a volume-limited galaxy sample from the Kilo Degree Survey Data Release 3. The k-Nearest Neighbour technique is adapted to take into account the probability density functions (PDFs) of photometric redshifts in our calculations. This algorithm was tested on simulated KiDS tiles, showing its capability of recovering the relation between galaxy colour, luminosity and local environment. The characterization of the galaxy environment in G3C groups shows systematically steeper density contrasts for more massive groups. The red galaxy fraction gradients in these groups is evident for most of group mass bins. The density contrast of red galaxies is systematically higher at group centers when compared to blue galaxy ones. In addition, distinct group center definitions are used to show that our results are insensitive to center definitions. These results confirm the galaxy evolution scenario which environmental mechanisms are responsible for a slow quenching process as galaxies fall into groups and clusters, resulting in a smooth observed colour gradients in galaxy systems.