Abstract
We present new, high-angular resolution interferometric observations with the
Karl G. Jansky Very Large Array of $^12$CO $J=1-0$ line emission and 4-8 GHz
continuum emission in the strongly lensed, $z=2.3$ submillimetre galaxy, SMM
J21352-0102. Using these data, we identify and probe the conditions in $\sim
100$pc clumps within this galaxy, which we consider to be potential giant
molecular cloud complexes, containing up to half of the total molecular gas in
this system. In combination with far-infrared and submillimetre data, we
investigate the far-infrared/radio correlation, measuring $q_IR = 2.39 \pm
0.17$ across SMM J21352. We search for variations in the properties of the
interstellar medium throughout the galaxy by measuring the spatially-resolved
$q_IR$ and radio spectral index, $\alpha_radio$, finding ranges
$q_IR = 2.1, 2.6$ and $\alpha_radio = -1.5, -0.7$. We argue that
these ranges in $\alpha_radio$ and $q_IR$ may reflect variations in
the age of the ISM material. Using multi-$J$ $^12$CO data, we quantitatively
test a recent theoretical model relating the star-formation rate surface
density to the excitation of $^12$CO, finding good agreement between the
model and the data. Lastly, we study the Schmidt-Kennicutt relation, both
integrated across the system and within the individual clumps. We find small
offsets between SMM J21352 and its clumps relative to other star-forming galaxy
populations on the Schmidt-Kennicutt plot - such offsets have previously been
interpreted as evidence for a bi-modal star-formation law, but we argue that
they can be equally-well explained as arising due to a combination of
observational uncertainties and systematic biases in the choice of model used
to interpret the data.
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