The Star-Forming Histories of the Nucleus, Bulge, and Inner Disk of NGC 5102: Clues to the Evolution of a Nearby Lenticular Galaxy

TL;DR

This study investigates the star formation history of NGC 5102, revealing a young nucleus, an intermediate-age bulge, and an old disk, supporting the idea that it evolved from a barred disk galaxy through bar buckling.

Contribution

It provides detailed star formation histories of different galaxy components, linking structural features to galaxy evolution processes in a nearby lenticular galaxy.

Findings

Nucleus has a luminosity-weighted age of ~1 Gyr.

Bulge has a luminosity-weighted age of ~2 Gyr.

Disk has a luminosity-weighted age of ~10 Gyr.

Abstract

Long slit spectra recorded with GMOS on Gemini South are used to examine the star-forming history of the lenticular galaxy NGC 5102. Structural and supplemental photometric information are obtained from archival Spitzer [3.6] images. Comparisons with model spectra point to luminosity-weighted metallicities that are consistent with the colors of resolved red giant branch stars in the disk. The nucleus has a luminosity-weighted age at visible wavelengths of ~1 Gyr, and the integrated light is dominated by stars that formed over a time period of only a few hundred Myr. For comparison, the luminosity-weighted ages of the bulge and disk are ~2 Gyr and ~10 Gyr, respectively. The g'-[3.6] colors of the nucleus and bulge are consistent with the spectroscopically-based ages. In contrast to the nucleus, models that assume star-forming activity spanning many Gyr provide a better match to the spectra of the bulge and disk than simple stellar population models. Isophotes in the bulge have a disky shape, hinting that the bulge was assembled from material with significant rotational support. The star-forming histories of the bulge and disk are consistent with the bulge forming from the collapse of a long-lived bar, and it is suggested that the progenitor of NGC 5102 was a barred disk galaxy that morphed into a lenticular galaxy through the buckling of its bar.