Outer disks of lenticular galaxies

TL;DR

This study reveals that the outer disks of lenticular galaxies are predominantly old, challenging the idea that S0 galaxies formed recently through star formation quenching of spirals.

Contribution

The paper provides new observational evidence that the outer stellar disks of S0 galaxies are mostly old, questioning existing formation models.

Findings

Outer disks are mostly 8-15 Gyr old

Outer disks are often older than bulges

Challenges the paradigm of recent S0 formation

Abstract

By studying the stellar population properties along the radius in 15 nearby S0 galaxies, I have found that the outer stellar disks are mostly old, with the SSP-equivalent ages of 8-15 Gyr, being often older than the bulges. This fact puts into doubt a currently accepted paradigm that S0 galaxies have formed at z=0.4 by quenching star formation in spiral galaxies.