Le Département d'Électronique des Détecteurs et d'Informatique pour la Physique

I  will present and discuss the implications of  the main results obtained  during  my PhD thesis carried out  at CEA/AIM/Saclay and supervised  by Ph. André. My work  has been focused on characterizing the physical properties of  interstellar filaments imaged in nearby molecular clouds  with the Herschel Space Observatory as part of the  Gould Belt survey. 

The high quality and high dynamic range of the Herschel  SPIRE and PACS images, has revealed the ubiquity  of filaments in the interstellar medium. The omnipresence of filamentary structures in non-star-forming clouds as well as in  active  star forming regions indicates that filament  formation precedes any star formation activity. Moreover the correlation between the spatial distribution of prestellar  cores and  the filamentary structures of the clouds suggests  that filaments may  give the initial conditions for star  formation. 

In order to get insights into the formation and evolution of  interstellar  filaments I studied in details the properties of the radial column density profiles of a large sample of filaments detected in several nearby clouds. A surprising result of this analysis is the remarkably uniform central width of ~0.1 pc shared by all the filaments,   while they span more than three orders of magnitude in central column density. 

This characteristic   width of interstellar filaments may originate from their formation process, possibly related to  the dissipation of large-scale  turbulence in the cold interstellar medium. Follow-up molecular line  observations with the IRAM 30m telescope, show an  increase in the  non-thermal  velocity dispersion of the densest  filaments as a function of  their central column density. This suggests that   gravity is a major driver in the subsequent evolution of the dense, self gravitating filaments which grow in mass per unit length by  accretion of background   material while at the same time  fragmenting  into star-forming cores.