Spatially resolved CIII]$\lambda$1909 emission in Haro 11

TL;DR

This study presents the first high-resolution imaging of CIII] emission in a low-redshift star-forming galaxy, revealing that strong CIII] emission depends on galaxy morphology and high C/O ratios, not just metallicity or stellar mass.

Contribution

It provides the first CIII] imaging of Haro 11 and investigates the relationship between CIII] emission and galaxy properties, highlighting the importance of morphology and chemical abundance ratios.

Findings

CIII] emission strength is not correlated with stellar mass or dust attenuation.

High EW(C III]) clusters require extremely high C/O ratios in models.

Galaxy morphology influences the integrated CIII] emission strength.

Abstract

The CIII]1909 (hereafter, C III]) line is the strongest ultraviolet emission line after Ly$\alpha$ and is therefore of interest to high redshift studies of star-forming (SF) galaxies near the epoch of reionization. It is thought that C III] emission is strongest in galaxies with subsolar metallicity and low mass, however, spectral observations of numerous such galaxies at high and low redshift produce inconclusive or even contradictory results. We present the first ever C III ] imaging, obtained with HST/STIS for the low-redshift SF galaxy Haro 11. Cluster parameters like stellar mass, dust fraction and dust attenuation, and ionization parameter, obtained through spectral energy distribution fitting, show no correlation with the CIII] equivalent width (EW), which may be due to a combination of the limitation of the models and the age-homogeneity of the cluster population. Comparing the ratio of C III] emission line flux from individual clusters to that of H$\alpha$, [O III], and [O II] we find that the clusters with the highest EW(C III]) can be reconciled only with Cloudy models with an extremely high C/O ratio of $\ge$ 1.4(C/O)$_\odot$ for an ionizing population of single stars, binary stars, or a mixture of binary stars and active galactic nuclei. Given the point-like nature of strong C III], the integrated total strength of EW(C III]) becomes dependent on the morphology of the galaxy, which would explain the large scatter in EW(C III]) strengths, observed in galaxies with otherwise similar SF properties, and of similarly low metallicity and stellar mass.