About the linearity of the color-magnitude relation of early-type galaxies in the Virgo cluster

TL;DR

This study investigates the linearity of the color-magnitude relation in Virgo cluster early-type galaxies, finding it to be linear when excluding brightest and atypical galaxies, and discusses implications for galaxy formation.

Contribution

It provides a comprehensive reanalysis of the CMR in Virgo galaxies, confirming linearity under specific conditions and identifying unique properties of compact ellipticals.

Findings

The CMR is linear for most early-type galaxies when brightest and atypical systems are excluded.

Central regions of brightest galaxies follow the same linear relation.

Virgo hosts at least four compact ellipticals with distinct <mueff>-luminosity trends.

Abstract

We revisit the color-magnitude relation (CMR) of the Virgo cluster early-type galaxies in order to explore its alleged non-linearity. To this aim, we reanalyze the relation already published from data obtained within the ACS Virgo Cluster Survey of the Hubble Space Telescope, and perform our own photometry and analysis of the images of the 100 early-type galaxies observed as part of this survey. In addition, we compare our results with those reported in the literature from data of the Sloan Digital Sky Survey. We have found that when the brightest galaxies and untypical systems are excluded from the sample, a linear relation arises in agreement with what is observed in other groups and clusters. The central regions of the brightest galaxies also follow this relation. In addition, we notice that Virgo contains at least four compact elliptical galaxies besides the well known object VCC 1297 (NGC 4486B). Their locations in the <mueff>-luminosity diagram define a different trend to that followed by normal early-type dwarf galaxies, setting an upper limit in effective surface brightness and a lower limit in effective radius for their luminosities. Based on the distribution of different galaxy sub-samples in the color-magnitude and <mueff>-luminosity diagrams we draw some conclusions on their formation and the history of their evolution.