Deciphering Galactic Halos: A Detailed Review of Star Formation in NGC 5128 (Cen A)

TL;DR

This study reconstructs the star formation history of NGC 5128's halo using LPV stars, revealing episodic star formation linked to merger events and nuclear activity, providing new insights into its complex evolution.

Contribution

It offers the first detailed SFH of NGC 5128's outer halo based on LPV stars, highlighting multiple star formation episodes and their connection to galaxy interactions.

Findings

Star formation peaks at ~800 Myr, 3.8 Gyr, and 6.3 Gyr ago.

Similar SFHs in two halo regions suggest synchronized evolutionary events.

Evidence supports merger and jet-induced star formation scenarios.

Abstract

NGC 5128 (Centaurus A), the closest giant elliptical galaxy outside the Local Group to the Milky Way, is one of the brightest extragalactic radio sources. It is distinguished by a prominent dust lane and powerful jets, driven by a supermassive black hole at its core. Using previously identified long-period variable (LPV) stars from the literature, this study aims to reconstruct the star formation history (SFH) of two distinct regions in the halo of NGC 5128. These regions reveal remarkably similar SFHs, despite being located about 28 kpc apart on opposite sides of the galaxy's center. In Field 1, star formation rates (SFRs) show notable increases at approximately 800 Myr and 3.8 Gyr ago. Field 2 exhibits similar peaks at these times, along with an additional rise around 6.3 Gyr ago. The increase in SFR around 800 Myr ago is consistent with earlier research suggesting a merger event. Since no LPV catalog exists for the central region of NGC 5128, we focused our investigation on its outer regions, which has provided new insights into the complex evolutionary history of this cornerstone galaxy. The SFH traced by LPVs supports a scenario in which multiple events of nuclear activity have triggered episodic, jet-induced star formation.