Unravelling multi-temperature dust populations in the dwarf galaxy Holmberg II

TL;DR

This study analyzes dust emission in Holmberg II, revealing multiple dust populations with distinct temperatures and their relation to FUV intensities, enhancing understanding of dust properties in dwarf galaxies.

Contribution

The paper introduces a method to identify multiple dust populations with different temperatures in Holmberg II using IR data, independent of location.

Findings

Dust spectra can be modeled by multiple temperature components.

Cold dust temperature correlates with FUV intensity at certain locations.

Different dust populations are spatially independent within the galaxy.

Abstract

Holmberg II - a dwarf galaxy in the nearby M81 group - is a very informative source of distribution of gas and dust in the interstellar discs. High-resolution observations in the infrared (IR) allows us to distinguish isolated star-forming regions, photodissociation (PDR) and HII regions, remnants of supernovae (SNe) explosions and, as such, can provide information about more relevant physical processes. In this paper we analyse dust emission in the wavelength range 4.5 to 160 micron using the data from IR space observatories at 27 different locations across the galaxy. We observe that the derived spectra can be represented by multiple dust populations with different temperatures, which are found to be independent of their locations in the galaxy. By comparing the dust temperatures with the far ultraviolet (FUV) intensities observed by the UVIT instrument onboard AstroSat, we find that for locations showing a 100 micron peak, the temperature of cold (20 to 30 K) dust grains show a dependence on the FUV intensities, while such dependence is not observed for the other locations. We believe that the approach described here can be a good tool in revealing different dust populations in other nearby galaxies with available high spatial resolution data.