Probing the Circumnuclear Stellar Populations of Starburst Galaxies in the Near-infrared

TL;DR

This study uses near-infrared spectroscopy to analyze stellar populations in four starburst galaxies, revealing dominant young/intermediate stars, circumnuclear star formation rings, and effects of galaxy interactions on metallicity.

Contribution

It provides a detailed spatial analysis of stellar populations in starburst galaxies using updated models and identifies the impact of galaxy mergers on stellar metallicity and population distribution.

Findings

NIR light is dominated by young/intermediate stellar populations.

Detection of circumnuclear star formation rings and secondary nucleus.

Galaxy interactions influence metallicity and stellar population ages.

Abstract

We employ the NASA Infrared Telescope Facility's near-infrared spectrograph SpeX at 0.8-2.4$\mu$m to investigate the spatial distribution of the stellar populations (SPs) in four well known Starburst galaxies: NGC34, NGC1614, NGC3310 and NGC7714. We use the STARLIGHT code updated with the synthetic simple stellar populations models computed by Maraston (2005, M05). Our main results are that the NIR light in the nuclear surroundings of the galaxies is dominated by young/intermediate age SPs ($t \leq 2\times10^9$yr), summing from $\sim$40\% up to 100\% of the light contribution. In the nuclear aperture of two sources (NGC1614 and NGC3310) we detected a predominant old SP component ($t > 2\times10^9$yr), while for NGC34 and NGC7714 the younger component prevails. Furthermore, we found evidence of a circumnuclear star formation ring-like structure and a secondary nucleus in NGC1614, in agreement with previous studies. We also suggest that the merger/interaction experienced by three of the galaxies studied, NGC1614, NGC3310 and NGC7714 can explain the lower metallicity values derived for the young SP component of these sources. In this scenario the fresh unprocessed metal poorer gas from the destroyed/interacting companion galaxy is driven to the centre of the galaxies and mixed with the central region gas, before star formation takes place. In order to deepen our analysis, we performed the same procedure of SP synthesis using Maraston (2011, M11) EPS models. Our results show that the newer and higher resolution M11 models tend to enhance the old/intermediate age SP contribution over the younger ages.