Cluster-green galaxy correlations: where do these galaxies live?

TL;DR

This study investigates the spatial distribution of green valley galaxies relative to galaxy systems using simulations and observational data, revealing their preference for outskirts and environmental influence on quenching.

Contribution

It combines hydrodynamical simulations and SDSS data to analyze green valley galaxy locations, highlighting environmental effects on galaxy evolution.

Findings

GV galaxies are more common in the outskirts of galaxy systems.

The distribution of GV galaxies supports environmental quenching scenarios.

Simulation and observational data show consistent trends in GV galaxy distribution.

Abstract

Green valley (GV) galaxies are thought to represent a transitional population between star-forming and quiescent systems. However, their spatial distribution relative to galaxy systems remains unclear, particularly in relation to the large-scale environmental influence on galaxy quenching. We aim to determine whether GV galaxies preferentially inhabit specific environments within galaxy systems. We analyse the spatial distribution of GV galaxies using the cluster-galaxy cross-correlation function (CCF), based on the hydrodynamical simulation Illustris TNG300-1 (TNG) and observational data from the Sloan Digital Sky Survey (SDSS). Galaxy systems with $\log(M_{200}/M_{\odot}) \geq 13.5$ are used as cluster centres, while galaxies classified as blue, green, or red serve as tracers for the correlation analysis. In TNG, GV galaxies show an increasing relative fraction with cluster-centric distance, peaking in the outskirts, particularly for low-mass galaxies and haloes, and in some cases the GV fraction exceeds that of red galaxies. SDSS data reveal qualitatively similar trends, with the GV fraction remaining below that of red galaxies at all scales. Mock catalogues built from TNG and matched to SDSS selection functions reproduce the observational signal, indicating that projection effects drive the differences between datasets. GV galaxies preferentially reside in the outskirts of galaxy systems as satellites bound to the central halo, supporting a scenario in which they are transitioning objects influenced by environmental quenching.