Cold dust and young starbursts: spectral energy distributions of Herschel SPIRE sources from the HerMES survey

TL;DR

This study analyzes the spectral energy distributions of 68 Herschel-detected galaxies to evaluate existing models and introduces new templates for better fitting diverse galaxy types, revealing insights into dust properties and starburst activity.

Contribution

It demonstrates the need for new SED templates for cold dust and young starbursts and assesses the effectiveness of existing models on Herschel data.

Findings

Many galaxies fit existing IR templates, but about half require new templates.

Herschel 500 μm sources have the highest dust masses.

Model predictions align better with data up to 70 μm than at 500 μm.

Abstract

We present spectral energy distributions (SEDs) for 68 Herschel sources detected at 5-sigma at 250, 350 and 500 mu in the HerMES SWIRE-Lockman field. We explore whether existing models for starbursts, quiescent star-forming galaxies and for AGN dust tori are able to model the full range of SEDs measured with Herschel. We find that while many galaxies (~ 56 %) are well fitted with the templates used to fit IRAS, ISO and Spitzer sources, for about half the galaxies two new templates are required: quiescent ('cirrus') models with colder (10-20 K) dust, and a young starburst model with higher optical depth than Arp 220. Predictions of submillimetre fluxes based on model fits to 4.5-24 mu data agree rather poorly with the observed fluxes, but the agreement is better for fits to 4.5-70 mu data. Herschel galaxies detected at 500 mu tend to be those with the very highest dust masses.