The Cold Dust Content of the Nearby Galaxies IC 5325, NGC 7496, NGC 7590, and NGC 7599

TL;DR

This study investigates the cold dust content in four nearby star-forming galaxies by constructing extensive spectral energy distributions from ultraviolet to radio wavelengths and modeling them to identify and quantify very cold dust components.

Contribution

It combines multi-wavelength observations and SED modeling to detect and estimate the mass of very cold dust in galaxies, highlighting its presence despite being faint and difficult to observe.

Findings

Hints of very cold dust in NGC 7496 and NGC 7590.

Warm dust dominates the total dust mass.

Multi-wavelength SED modeling constrains cold dust properties.

Abstract

Star-forming galaxies are rich reservoirs of dust, both warm and cold. But the cold dust emission is faint alongside the relatively bright and ubiquitous warm dust emission. Recently, evidence for a very cold dust component has also been revealed via millimeter/submillimeter photometry of some galaxies. This component, despite being the most massive of the three dust components in star-forming galaxies, is by virtue of its very low temperature, faint and hard to detect together with the relatively bright emission from warmer dust. Here we analyze the dust content of a carefully selected sample of four galaxies detected by IRAS, WISE, and SPT, whose spectral energy distributions (SEDs) were modeled to constrain their potential cold dust content. Low-frequency radio observations using the GMRT were carried out to segregate cold dust emission from non-thermal emission in millimeter/submillimeter wavebands. We also carried out AstroSat/UVIT observations for some galaxies to constrain their SED at shorter wavelengths so as to enforce energy balance for the SED modeling. We constructed their SEDs across a vast wavelength range (extending from ultraviolet to radio frequencies) by assembling global photometry from GALEX FUV+NUV, UVIT, Johnson BRI, 2MASS, WISE, IRAC, IRAS, AKARI, ISOPHOT, Planck HFI, SPT, and GMRT. The SEDs were modeled with CIGALE to estimate their basic properties, in particular to constrain the masses of their total and very cold dust components. Although the galaxies' dust masses are dominated by warmer dust, there are hints of very cold dust in two of the targets, NGC 7496 and NGC 7590.