The Compact Star-Forming Complex at the Heart of NGC 253

TL;DR

This study analyzes the properties and star formation activity of a compact star-forming complex in NGC 253's center, revealing young stellar populations, Wolf-Rayet stars, and rapid mass growth potential.

Contribution

It provides detailed spectroscopic insights into the age, composition, and star formation dynamics of the central complex in NGC 253, highlighting its rapid stellar mass accumulation.

Findings

Presence of young star pockets <8 Myr old.

Detection of Wolf-Rayet star populations.

Estimated rapid stellar mass doubling times.

Abstract

We discuss integral field spectra of the compact star-forming complex that is the brightest near-infrared (NIR) source in the central regions of the starburst galaxy NGC 253. The spectra cover the H and K passbands and were recorded with the Gemini NIR Spectrograph during sub-arcsec seeing conditions. Absorption features in the spectrum of the star-forming complex are weaker than in the surroundings. An absorption feature is found near 1.78um that coincides with the location of a C2 bandhead. Emission lines of Brgamma, [FeII], and HeI2.06um do not track the NIR continuum light. Pockets of star-forming activity that do not have associated concentrations of red supergiants, and so likely have ages < 8 Myr, are found along the western edge of the complex, and there is evidence that one such pocket contains a rich population of Wolf-Rayet stars. Unless the star-forming complex is significantly more metal-poor than the surroundings, then a significant fraction of its total mass is in stars with ages < 8 Myr. If the present-day star formation rate is maintained then the time scale to double its stellar mass ranges from a few Myr to a few tens of Myr, depending on the contribution made by stars older than ~ 8 Myr. If -- as suggested by some studies -- the star-forming complex is centered on the galaxy nucleus, then the nucleus of NGC 253 is currently experiencing a phase of rapid growth in its stellar mass.