UVIT imaging of WLM : Demographics of star forming regions in the nearby dwarf irregular galaxy

TL;DR

This study uses UVIT multi-band observations to analyze star forming regions in the dwarf galaxy WLM, revealing their distribution, temperature, hierarchical structure, and recent star formation activity.

Contribution

First detailed UV imaging analysis of WLM's star forming regions, linking UV emission, temperature, and spatial distribution to star formation processes.

Findings

UV emission extends up to 1.7 kpc in WLM.

Identified hot stellar complexes with T > 17500 K.

Star formation rate estimated at ~0.008 solar masses per year.

Abstract

We present a study of star forming regions and its demographics in the nearby dwarf irregular galaxy WLM using the Ultra-Violet Imaging Telescope (UVIT) multi band observations in three filters F148W, N245M and N263M. We find that the UV emission is extended at least up to 1.7 kpc, with the NUV emission more extended than the FUV. We create UV color maps ((F148W$-$N245M) and (F148W$-$N263M)) to study the temperature morphology of young stellar complexes with the help of theoretical models. We identify several complexes with temperature T $>$ 17500 K which are likely to be the OB associations present in the galaxy. These complexes show good spatial correlation with the H$\alpha$ emitting regions, H$~$I distribution and HST detected hot stars. The hot star forming regions are found to be clumpy in nature and show a hierarchical structure, with sizes in the range of 4 - 50 pc, with a large number with sizes $<$ 10 pc. The south western part of the galaxy shows many hot star forming regions, high level of H$\alpha$ emission and low column density of H$~$I which altogether denote a vigorous recent star formation. WLM is likely to have a large fraction of low mass compact star forming regions with mass M $< 10^3 M_{\odot}$, in agreement with the size and mass of the CO clouds. We estimate the star formation rate of WLM to be $\sim$ 0.008 $M_{\odot}/yr$, which is similar to the average value measured for nearby dwarf irregular galaxies.