Galactic star formation with NIKA2 (GASTON): Filament convergence and
  its link to star formation
  In the past decade filaments have been recognised as a major structural
element of the interstellar medium, the densest of these filaments hosting the
formation of most stars. In some star-forming molecular clouds converging
networks of filaments, also known as hub filament systems, can be found. These
hubs are believed to be preferentially associated to massive star formation. As
of today, there are no metrics that allow the systematic quantification of a
filament network convergence. Here, we used the IRAM 30m NIKA2 observations of
the Galactic plane from the GASTON large programme to systematically identify
filaments and produce a filament convergence parameter map. We use such a map
to show that: i. hub filaments represent a small fraction of the global
filament population; ii. hubs host, in proportion, more massive and more
luminous compact sources that non-hubs; iii. hub-hosting clumps are more
evolved that non-hubs; iv. no discontinuities are observed in the properties of
compact sources as a function of convergence parameter. We propose that the
rapid global collapse of clumps is responsible for (re)organising filament
networks into hubs and, in parallel, enhancing the mass growth of compact
sources.
