The Herschel-ATLAS: The dust energy balance in the edge-on spiral galaxy UGC 4754

TL;DR

This study uses Herschel observations and radiative transfer modeling to examine the dust energy balance in the edge-on galaxy UGC 4754, revealing significant underestimation of FIR emission by models.

Contribution

It demonstrates that current radiative transfer models underestimate FIR emission in edge-on galaxies, suggesting highly obscured star formation as a key factor.

Findings

Radiative transfer models underestimate FIR emission by a factor of two to three.

Discrepancies are not due to FIR emissivity underestimation.

Highly obscured star formation likely explains the FIR excess.

Abstract

We use Herschel PACS and SPIRE observations of the edge-on spiral galaxy UGC 4754, taken as part of the H-ATLAS SDP observations, to investigate the dust energy balance in this galaxy. We build detailed SKIRT radiative models based on SDSS and UKIDSS maps and use these models to predict the far-infrared emission. We find that our radiative transfer model underestimates the observed FIR emission by a factor of two to three. Similar discrepancies have been found for other edge-on spiral galaxies based on IRAS, ISO, and SCUBA data. Thanks to the good sampling of the SED at FIR wavelengths, we can rule out an underestimation of the FIR emissivity as the cause for this discrepancy. Instead we support highly obscured star formation that contributes little to the optical extinction as a more probable explanation.