The HI dominated Low Surface Brightness Galaxy KKR17

TL;DR

This study investigates the properties of the low surface brightness galaxy KKR 17, revealing its gas-rich nature, recent star formation activity, and complex kinematic features in its HII regions through imaging and spectrophotometry.

Contribution

It provides detailed analysis of KKR 17's stellar populations, metallicity, and star formation, highlighting the galaxy's gas dominance and the complexity of its star-forming regions.

Findings

KKR 17 is gas-rich with low stellar mass.

The galaxy's metallicity is 12 + (O/H) = 8.0 ± 0.1.

Star formation rate is approximately 0.21 M_sun/yr.

Abstract

We present new narrow-band (H$\alpha$ and [OIII]) imagings and optical spectrophotometry of HII regions for a gas-rich low surface brightness irregular galaxy, KKR 17. The central surface brightness of the galaxy is $\mu_0(B)$ = 24.15 $\pm$0.03 mag~sec$^{-2}$. The galaxy was detected by \emph{Arecibo Legacy Fast ALFA survey} (ALFALFA), and its mass is dominated by neutral hydrogen (HI) gas. In contrast, both the stellar masses of the bright HII and diffuse stellar regions are small. In addition, the fit to the spectral energy distribution to each region shows the stellar populations of HII and diffuse regions are different. The bright HII region contains a large fraction of O-type stars, revealing the recent strong star formation, whereas the diffuse region is dominated by median age stars, which has a typical age of $\sim$ 600 Myrs. Using the McGaugh's abundance model, we found that the average metallicity of KKR 17 is 12 + (O/H) = 8.0 $\pm$ 0.1. The star formation rate of KKR 17 is 0.21$\pm$0.04 M$_{\odot}$/yr, which is $\sim$1/5 of our Milky Way's. Based on the analysis results to young stellar clusters in HII region, it is found that the bright HII region showed two sub-components with different velocities and metallicities. This may be caused by the outflow of massive stars or merging events. However, the mechanism of triggering star formation in the HII region is still uncertain.