Properties of Stellar Populations in Isolated Lenticular Galaxies

TL;DR

This study investigates the stellar populations of isolated lenticular galaxies using spectral observations, revealing diverse formation epochs and similar ages in bulges and discs, influenced by external gas accretion.

Contribution

It provides detailed measurements of stellar ages, metallicities, and kinematics in isolated S0 galaxies, highlighting their varied formation histories and the role of external gas accretion.

Findings

Stellar ages range from 1.5 to 15 Gyr, indicating diverse formation epochs.

Isolated S0 galaxies often have similar ages in bulges and discs.

Morphological features like lenses and rings share stellar population properties with discs.

Abstract

In this paper we present the results of long-slit spectral observations for a sample of isolated lenticular galaxies, made with the SCORPIO and SCORPIO-2 spectrographs of the 6-meter BTA telescope of the SAO RAS. By applying full spectral fitting technique using the stellar population evolutionary synthesis models, we have measured the radial profiles of the stellar line-of-sight velocity as well as the velocity dispersion, SSP-equivalent age and SSP-equivalent metallicity of stars along the radius in 12 targets. The resulting averaged ages of the stellar population in bulges and discs cover an entire range of possible values from 1.5 to 15 Gyr which indicates the absence of a certain formation epoch for the structural components in the isolated lenticular galaxies, unlike in the members of clusters and rich groups: they could have been formed at a redshift of $z>2$ as well as only a few billion years ago. Unlike S0 galaxies in more dense environments, the isolated galaxies typically have the same age of stars in the bulges and discs. The disc-embedded lenses and rings of increased stellar brightness, identified from the photometry in 7 of 11 galaxies, do not differ strongly from the stellar discs as concerning the properties of stellar populations and stellar velocity dispersion. We conclude that the final shaping of the morphological type of a lenticular galaxy in complete isolation is critically dependent on the possible regimes of cold-gas accretion from outside.