Photometric redshifts as a tool to study the Coma cluster galaxy populations

TL;DR

This study uses photometric redshift techniques on deep multi-band images to analyze the faint galaxy populations in the Coma cluster, revealing variations in galaxy types and star formation activity across different regions.

Contribution

It applies photometric redshift methods to derive the galaxy luminosity function in multiple bands, including the faint u* band, and investigates spatial distribution and star formation in the cluster.

Findings

Faint end slope of the u* band GLF increases towards the cluster outskirts.

Late type galaxies are clustered in the outskirts with associated X-ray substructures.

The u* band GLF steepens in the outer regions, indicating recent star formation.

Abstract

We investigate the Coma cluster galaxy luminosity function (GLF) at faint magnitudes, in particular in the u* band by applying photometric redshift techniques applied to deep u*, B, V, R, I images covering a region of ~1deg2 (R 24). Global and local GLFs in the B, V, R and I bands obtained with photometric redshift selection are consistent with our previous results based on a statistical background subtraction. In the area covered only by the u* image, the GLF was also derived after applying a statistical background subtraction. The GLF in the u* band shows an increase of the faint end slope towards the outer regions of the cluster (from alpha~1 in the cluster center to alpha~2 in the cluster periphery). This could be explained assuming a short burst of star formation in these galaxies when entering the cluster. The analysis of the multicolor type spatial distribution reveals that late type galaxies are distributed in clumps in the cluster outskirts, where X-ray substructures are also detected and where the GLF in the u* band is steeper.