The width of filamentary structures in the ISM sets the scale for fragmentation and core evolution. Whether this width is typical or changes with the environmental conditions has been a decade-long debate that is still not settled.
We characterize the physical properties of velocity-coherent structures in 7 star-forming regions in Orion using ALMA observations of N2H+ (1 ? 0) at a 4.5” resolution: OMC-1, OMC-2, OMC-3, OMC-4, LDN1641-North, NGC 2023 and Flame Nebula. These regions have been selected as representative of low-, intermediate- and high-mass star-forming environments. We analyze the kinematic parameters and the column density distribution derived from the molecular emission to infer the widths, line masses, non-thermal motions and densities of 150 velocity-coherent structures, classically referred to as ‘dense fibers’.
The distribution of their widths shows variability among regions, with values ranging from 0.03 pc to 0.09 pc, narrower than 0.1 pc, typical filament width of the Herschel filaments.
The origin of this difference is connected to the different density regimes probed in these regions, for which dense fibers are natural evolution of larger scale filaments in a more complex environment and their widths (FWHM) show a clear anticorrelation with the density (n).