Dissecting the super-critical filaments embedded in the 0.5 pc subsonic region of Barnard 5

TL;DR

This study provides a detailed analysis of two super-critical filaments in Barnard 5, revealing their physical properties, stability conditions, and internal structure, with implications for star formation processes.

Contribution

It offers high-resolution observational characterization of super-critical filaments, including their density profiles, widths, and stability, which advances understanding of filament evolution and star formation.

Findings

Filaments are highly super-critical with M/L ~80-150 M_sun/pc.

Filament widths are ~0.03 pc, about twice the flat inner radius.

An empirical relation links density, radius, and density profile exponent.

Abstract

We characterize in detail the two ~0.3 pc long filamentary structures found within the subsonic region of Barnard 5. We use combined GBT and VLA observations of the molecular lines NH$_3$(1,1) and (2,2) at a resolution of 1800 au, as well as JCMT continuum observations at 850 and 450 $\mu$m at a resolution of 4400 au and 3000 au, respectively. We find that both filaments are highly super-critical with a mean mass per unit length, $M/L$, of ~80 M$_\odot$ pc$^{-1}$, after background subtraction, with local increases reaching values of ~150 M$_\odot$ pc$^{-1}$. This would require a magnetic field strength of ~500 $\mu$G to be stable against radial collapse. We extract equidistant cuts perpendicular to the spine of the filament and fit a modified Plummer profile as well as a Gaussian to each of the cuts. The filament widths (deconvolved FWHM) range between 6500-7000 au (~0.03 pc) along the filaments. This equals ~2.0 times the radius of the flat inner region. We find an anti-correlation between the central density and this flattening radius, suggestive of contraction. Further, we also find a strong correlation between the power-law exponent at large radii and the flattening radius. We note that the measurements of these three parameters fall in a plane and derive their empirical relation. Our high-resolution observations provide direct constraints of the distribution of the dense gas within super-critical filaments showing pre- and protostellar activity.