The Core Mass Function Across Galactic Environments. II. Infrared Dark
  Cloud Clumps
  We study the core mass function (CMF) within 32 dense clumps in seven
infrared dark clouds (IRDCs) with the Atacama Large Millimeter/submillimeter
Array (ALMA) via 1.3~mm continuum emission at a resolution of $\sim$1". We have
identified 107 cores with the dendrogram algorithm, with a median radius of
about 0.02 pc. Their masses range from 0.261 to 178 $M_{\odot}$. After applying
completeness corrections, we fit the combined IRDC CMF with a power law of the
form $d N / d\:{\rm log} M \propto M^{-\alpha}$ and derive an index of
$\alpha\simeq0.86\pm0.11$ for $M \geq 0.79\:M_\odot$ and
$\alpha\simeq0.70\pm0.13$ for $M\geq 1.26\:M_\odot$, which is a significantly
more top-heavy distribution than the Salpeter stellar initial mass function
(IMF) index of 1.35. We also make a direct comparison of these IRDC clump CMF
results to those measured in the more evolved protocluster G286 derived with
similar methods, which have $\alpha\simeq1.29\pm0.19$ and $1.08\pm0.27$ in
these mass ranges, respectively. These results provide a hint that, especially
for the $M\geq 1.26\:M_\odot$ range where completeness corrections are modest,
the CMF in high pressure, early-stage environments of IRDC clumps may be
top-heavy compared to that in the more evolved, global environment of the G286
protoclusters. However, larger samples of cores probing these different
environments are needed to better establish the robustness of this potential
CMF variation.
