Emergence of high-mass stars in complex fiber networks (EMERGE) IV. Environmental dependence of the fiber widths

Despite their variety of scales throughout the interstellar medium, filaments in nearby low-mass clouds show a characteristic width of ~ 0.1 pc from the analysis of { Herschel} observations. The origin of this characteristic width, however, has been a matter of intense discussions during the last decade. We explored a possible variation in this typical width with the EMERGE Early ALMA Survey, which includes seven star-forming regions in Orion (OMC-1/-2/-3/-4 South, LDN 1641N, NGC 2023, Flame Nebula). These targets, which exhibit different physical conditions, star formation histories, mass, and density regimes, were homogeneously surveyed at a resolution of ~ 2000 au in N₂H⁺ (1$-$0) with ALMA+IRAM-30m observations. We characterised the column density and temperature radial profiles of the 152 fibers identified in the survey using the automatic fitting routine FilChap. These Orion fibers show a departure from the isothermal condition with significant outward temperature gradients with ∇ TK > 30 K pc⁻¹. They also show a median full width at half maximum ($FWHM$) of ~ 0.05 pc, with a corresponding median aspect ratio of ~2. More relevantly, we observe a systematic variation in these fiber $FWHM$ between different regions in our sample, and a direct inverse dependence of these $FWHM$ on their central column density, N₀, above 10²² cm⁻². This dependency agrees with the expected N₀-FWHM anti-correlation predicted in previous theoretical studies. Our homogeneous analysis returns the first observational evidence of an intrinsic and systematic variation in the fiber widths across different star-forming regions. While sharing comparable mass, length, and kinematic properties in all of our targets, fibers appear to adjust their $FWHM$ to their density and to the pressure in their host environment.