A tale of two nearby dwarf irregular galaxies WLM and IC 2574 -- as revealed by UVIT

TL;DR

This UV study of the dwarf irregular galaxies WLM and IC 2574 reveals detailed properties of their star-forming regions, including sizes, shapes, orientations, and age-related spatial distributions, enhancing understanding of star formation in small galaxies.

Contribution

First UV imaging analysis of WLM and IC 2574 highlighting their star-forming clump properties and spatial distributions, with insights into hierarchical structures and orientations.

Findings

Identified 180 and 782 star-forming clumps in WLM and IC 2574.

Clump sizes range from 7-30 pc in WLM and 26-150 pc in IC 2574.

Younger clumps are smaller and located in specific galaxy regions.

Abstract

We present an ultra-violet study of two nearby dwarf irregular galaxies WLM and IC~2574, using the Far-UV and Near-UV data from the Ultra-Violet Imaging Telescope (UVIT). We used the F148W band Far-UV images and identified 180 and 782 young star-forming clumps in WLM and IC~2574, respectively. The identified clumps have sizes between 7 - 30 pc in WLM and 26 - 150 pc in IC~2574. We noticed more prominent hierarchical splitting in the structure of star-forming regions at different flux levels in IC~2574 than WLM. We found that the majority of the clumps have elongated shapes in the sky plane with ellipticity ($\epsilon$) greater than 0.6 in both the galaxies. The major axis of the identified clumps is found to show no specific trend of orientation in IC~2574, whereas in WLM the majority are aligned along south-west to north-east direction. We estimated (F148W$-$N242W) colour for the clumps identified in WLM and noticed that the younger ones (with (F148W$-$N242W) $<-0.5$) are smaller in size ($<10$ pc) and are located mostly in the southern half of the galaxy between galactocentric radii 0.4 - 0.8 kpc.