Optical/Near-IR spatially resolved study of the H II galaxy Tol 02

TL;DR

This study provides a detailed spatially resolved analysis of stellar populations in the low-metallicity galaxy Tol 02, revealing its complex star formation history and stellar components through multi-band imaging.

Contribution

It offers a comprehensive characterization of Tol 02's stellar populations and star formation activity using deep multi-band imaging and comparison with stellar population models.

Findings

Tol 02 has a 1.5 Gyr old disk with young stellar clumps.

Six clumps are 10 Myr old dominated by Red Supergiants.

Star formation appears stochastic and simultaneous over short timescales.

Abstract

The main goal of this study is to characterise the stellar populations in very low metallicity galaxies. We have obtained broad U, B, R, I, J, H, K, intermediate Str\"omgren y and narrow H{\alpha} and [OIII] deep images of the Wolf-Rayet, Blue Compact Dwarf, H II galaxy Tol 02. We have analysed the low surface brightness component, the stellar cluster complexes and the H II regions. The stellar populations in the galaxy have been characterised by comparing the observed broad band colours with those of single stellar population models. The main results are consistent with Tol 02 being formed by a 1.5 Gyr old disk component at the centre of which a group of 8 massive $>10^4 \, M_{\odot}$ stellar cluster clumps is located. Six of these clumps are 10 Myr old and their near infrared colours suggest that their light is dominated by Red Supergiant stars, the other two are young Wolf-Rayet cluster candidates of ages 3 and 5 Myr respectively. 12 H II regions in the star-forming region of the galaxy are also identified. These are immersed in a diffuse H{\alpha} and [OIII] emission that spreads towards the North and South covering the old stellar disk. Our spatial-temporal analysis shows that star formation is more likely stochastic and simultaneous within short time scales. The mismatch between observations and models cannot be attributed alone to a mistreat of the RSG phase and still needs to be further investigated.