Ghosts in the Attic: Mapping the Stellar Content of the S0 Galaxy NGC 5102

TL;DR

This study maps the stellar populations of the S0 galaxy NGC 5102, revealing its star formation history, spatial distribution of different star types, and evidence of past interactions affecting its structure.

Contribution

It provides a detailed spatial analysis of stellar populations and star formation history in NGC 5102, including the identification of a possible remnant of a companion galaxy.

Findings

Main sequence stars detected throughout the disk, mostly in the south.

Star formation rate increased in the past 1 Gyr, especially in the center.

Identification of a stellar clump likely from a past galaxy interaction.

Abstract

The spatial distribution of stars in the nearby S0 galaxy NGC 5102 is investigated using images obtained with WIRCam and MegaCam on the Canada-France-Hawaii Telescope. With the exception of gaps between detector elements, the entire galaxy is surveyed in r' and i', while the J and Ks data extend out to 6 kpc (7 disk scale lengths). A modest population of main sequence (MS) stars with M_V < -3.5 and ages 70 Myr are detected throughout the disk, with the majority located in the southern half of the galaxy. The ratio of C stars to bright M giants is consistent with an overall increase in the star formation rate within the past 1 Gyr. Star-forming activity during the interval 0.1 - 2 Gyr was more centrally concentrated than during the past 100 Myr. The structure of the disk changes near 5 kpc (5.5 disk scale lengths). RSGs and bright AGB stars are traced out to a radius of 14 kpc (15.6 scale lengths) along the southern portion of the major axis, while a tentative detection is also made of bright AGB stars at a projected distance of 16 kpc along the south east minor axis. A large clump of AGB stars that subtends an arcmin is identified to the west of the galaxy center. It is argued that this is the remnant of a companion galaxy that triggered past episodes of elevated star-forming activity.