Connecting Young Star Clusters to CO Molecular Gas in NGC 7793 with
  ALMA-LEGUS
  We present an investigation of the relationship between giant molecular cloud
(GMC) properties and the associated stellar clusters in the nearby flocculent
galaxy NGC 7793. We combine the star cluster catalog from the HST LEGUS (Legacy
ExtraGalactic UV Survey) program with the 15 parsec resolution ALMA CO(2-1)
observations. We find a strong spatial correlation between young star clusters
and GMCs such that all clusters still associated with a GMC are younger than 11
Myr and display a median age of 2 Myr. The age distribution increases gradually
as the cluster-GMC distance increases, with star clusters that are spatially
unassociated with molecular gas exhibiting a median age of 7 Myr. Thus, star
clusters are able to emerge from their natal clouds long before the timescale
required for clouds to disperse. To investigate if the hierarchy observed in
the stellar components is inherited from the GMCs, we quantify the amount of
clustering in the spatial distributions of the components and find that the
star clusters have a fractal dimension slope of $-0.35 \pm 0.03$, significantly
more clustered than the molecular cloud hierarchy with slope of $-0.18 \pm
0.04$ over the range 40-800 pc. We find, however, that the spatial clustering
becomes comparable in strength for GMCs and star clusters with slopes of
$-0.44\pm0.03$ and $-0.45\pm0.06$ respectively, when we compare massive
($>$10$^5$ M$_{\odot}$) GMCs to massive and young star clusters. This shows
that massive star clusters trace the same hierarchy as their parent GMCs, under
the assumption that the star formation efficiency is a few percent.
