Erik Rosolowsky edited Introduction.tex  about 8 years ago

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When the molecular ISM is partitioned into molecular clouds, the mass distribution of the population also shows a characteristic truncation mass \citep{Williams_1997,Rosolowsky_2005a} and the characteristic mass also evolves with the changing properties of the galactic environment \cite{Rosolowsky_2007,Colombo_2014,Hughes_2015}. While assumed that these two characteristic masses are linked, this correlation has yet to be demonstrated. Furthermore, the characteristic masses of the molecular clouds and clusters have not been well linked back to the cloud formation process, though models of cloud formation should predict the resulting characteristic mass \citep[e.g.,]{Duarte_Cabral_2016,Pan_2016}. Several different cloud formation scenarios have been proposed \cite{Dobbs_2014} and the evolving characteristic mass provides a clear observational handle for evaluating those formation mechanisms.  The nearby galaxy M83 provides an excellent opportunity to evaluate the evolving mass distribution of molecular clouds in conjunction with the changing cluster properties. As the nearest ($D=4.8$~Mpc)\citep{Radburn_Smith_2011}, face-on, massive spiral galaxy, M83 is an obvious target for exploring molecular cloud properties. Archival Hubble Space Telescope data have already been analyzed, showing a significant change in both the fraction of star formation that results in bound clusters \citep{Silva_Villa_2013} and the changing characteristic masses of young massive cluster populations \citep{Adamo_2015}. This latter work found that the cluster mass distribution followed a Schechter function, i.e. a power-law mass distribution with an index of -2 and an exponential truncation at a characteristic mass. We therefore investigate whether the molecular cloud population, which must serve as the progenitors of these clouds a similar mass distribution with truncation. To explore this question, we utilize archival data from the Atacama Millimeter/Submillimeter Array (ALMA), which can providing exceptional imaging data of this nearby galaxy. In particular, we use the high-quality $^{12}$CO($1\to0$) data set observed as part of ALMA project 2012.1.00762.S (PI (PI:  A. Hirota).