Cold galaxies

TL;DR

This study uses Planck data to identify galaxies with exceptionally cold dust, confirming they have larger angular diameters and cold dust generally resides outside the optical galaxy, supporting theories about dust temperature and distribution.

Contribution

It provides observational evidence linking cold dust in galaxies to larger angular sizes and spatial distribution outside the optical regions.

Findings

Cold dust galaxies have larger 350 μm diameters.

Cold dust is typically located outside the optical galaxy.

Confirmed cold dust temperatures are 10-13 K.

Abstract

We use 350 mu angular diameter estimates from Planck to test the idea that some galaxies contain exceptionally cold (10-13 K) dust, since colder dust implies a lower surface brightness radiation field illuminating the dust, and hence a greater physical extent for a given luminosity. The galaxies identified from their spectral energy distributions as containing cold dust do indeed show the expected larger 350 mu diameters. For a few cold dust galaxies where Herschel data are available we are able to use submillimetre maps or surface brightness profiles to locate the cold dust, which as expected generally lies outside the optical galaxy.