On the Color Magnitude Relation of Early-type Galaxies

TL;DR

This study analyzes the color magnitude relation of 468 early-type galaxies in the Virgo Cluster, revealing a continuous, non-linear S-shaped relation across all colors, with increased scatter at intermediate luminosities, suggesting a common origin for dwarfs and giants.

Contribution

It provides the first detailed, model-independent analysis of the non-linear CMR in Virgo, confirming the relation's shape and scatter characteristics across multiple colors.

Findings

The CMR is continuous and S-shaped in all colors.

Scatter increases at intermediate luminosities.

Dwarfs and giants may share a common origin.

Abstract

In this letter we present a study of the color magnitude relation of 468 early-type galaxies in the Virgo Cluster with Sloan Digital Sky Survey imaging data. The analysis of our homogeneous, model-independent data set reveals that, in all colors (u-g, g-r, g-i, i-z) similarly, giant and dwarf early-type galaxies follow a continuous color magnitude relation (CMR) that is best described by an S-shape. The magnitude range and quality of our data allows us to clearly confirm that the CMR in Virgo is not linear. Additionally, we analyze the scatter about the CMR and find that it increases in the intermediate-luminosity regime. Nevertheless, despite this observational distinction, we conclude from the similarly shaped CMR of semi-analytic model predictions that dwarfs and giants could be of the same origin.