2011MNRAS.418..828H

The central star-forming region in a blue compact dwarf galaxy, II Zw 40, was observed in the 340-GHz (880-µm) band at ∼5 arcsec (250 pc) resolution with the Submillimetre Array (SMA). A source associated with the central star-forming complex was detected with a flux of 13.6±2.0 mJy. The structure is more extended than the beam in the east–west direction. The SMA 880-µm flux is analysed by using theoretical models of radio spectral energy distribution along with centimetre interferometric measurements in the literature. We find that (i) the SMA 880-µm flux is dominated (∼75 per cent) by free–free emission from the central compact star-forming region and (ii) the contribution from dust emission to the SMA 880-µm flux is at most 4±2.5 mJy. We also utilize our models to derive the radio–far-infrared (FIR) relation of the II Zw 40 centre, suggesting that free–free absorption at low frequencies (ν ≲ several GHz; λ ≳ several cm) and the spatial extent of dust affect the radio–FIR relation.