Luminosities of Barred and Unbarred S0 Galaxies

TL;DR

This study examines the luminosity differences between barred and unbarred S0 galaxies, revealing that more luminous S0s tend to be unbarred, suggesting a link between galaxy luminosity, morphology, and evolutionary processes.

Contribution

It provides new insights into the luminosity distribution of barred versus unbarred S0 galaxies and discusses implications for galaxy evolution and classification accuracy.

Findings

Luminous S0 galaxies are predominantly unbarred.

Unbarred S0s are on average ~0.4 mag brighter than barred S0s.

Evolutionary links between luminous S0s and elliptical galaxies are suggested.

Abstract

Lenticular galaxies with M_B < -21.5 are almost exclusively unbarred, whereas both barred and unbarred objects occur at fainter luminosity levels. This effect is observed both for objects classified in blue light, and for those that were classified in the infrared. This result suggests that the most luminous (massive) S0 galaxies find it difficult to form bars. As a result the mean luminosity of unbarred lenticular galaxies in both B and IR light is observed to be ~0.4 mag brighter than than that of barred lenticulars. A small contribution to the observed luminosity difference that is found between SA0 and SB0 galaxies may also be due to the fact that there is an asymmetry between the effects of small classification errors on SA0 and SB0 galaxies. An E galaxy might be misclassified as an S0, or an S0 as an E. However, an E will never be misclassified an SB0, nor will an SB0 ever be called an E. This asymmetry is important because elliptical (E) galaxies are typically twice as luminous as lenticular (S0) galaxies. The present results suggest that the evolution of luminous lenticular galaxies may be closely linked to that of elliptical galaxies, whereas fainter lenticulars might be more closely associated with ram-pressure stripped spiral galaxies. Finally it is pointed out that fine details of the galaxy formation process might account for some of the differences between the classifications of the same galaxy by individual competent morphologists.