FIR colours and SEDs of nearby galaxies observed with Herschel

TL;DR

This study analyzes infrared colours and spectral energy distributions of 51 nearby galaxies across various types, revealing differences in dust temperature, composition, and emission mechanisms related to galaxy activity and metallicity.

Contribution

It provides a comprehensive comparison of FIR colours and SEDs across galaxy types, highlighting how dust properties vary with star formation and metallicity.

Findings

Active galaxies have warmer FIR colours than spirals.

Ellipticals with radio sources show synchrotron-dominated FIR emission.

Cold dust temperature correlates with galaxy activity and metallicity.

Abstract

We present infrared colours (in the 25-500 mic spectral range) and UV to radio continuum spectral energy distributions of a sample of 51 nearby galaxies observed with SPIRE on Herschel. The observed sample includes all morphological classes, from quiescent ellipticals to active starbursts. Active galaxies have warmer colour temperatures than normal spirals. In ellipticals hosting a radio galaxy, the far-infrared (FIR) emission is dominated bynthe synchrotron nuclear emission. The colour temperature of the cold dust is higher in quiescent E-S0a than in star-forming systems probably because of the different nature of their dust heating sources (evolved stellar populations, X-ray, fast electrons) and dust grain properties. In contrast to the colour temperature of the warm dust, the f350/f500 index sensitive to the cold dust decreases with star formation and increases with metallicity, suggesting an overabundance of cold dust or an emissivity parameter beta<2 in low metallicity, active systems.