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