The Spatial Extent of (U)LIRGs in the Mid-infrared. I. The Continuum Emission
Résumé
We present an analysis of the extended mid-infrared (MIR) emission of the Great Observatories All-Sky LIRG Survey sample based on 5-15 mum low-resolution spectra obtained with the Infrared Spectrograph on Spitzer. We calculate the fraction of extended emission (FEE) as a function of wavelength for the galaxies in the sample, FEElambda, defined as the fraction of the emission which originates outside of the unresolved component of a source at a given distance. We find that the FEElambda varies from one galaxy to another, but we can identify three general types of FEElambda: one where FEElambda is constant, one where features due to emission lines and polycyclic aromatic hydrocarbons appear more extended than the continuum, and a third which is characteristic of sources with deep silicate absorption at 9.7 mum. More than 30% of the galaxies have a median FEElambda larger than 0.5, implying that at least half of their MIR emission is extended. Luminous Infrared Galaxies (LIRGs) display a wide range of FEE in their warm dust continuum (0