Tracing the general structure of Galactic molecular clouds using Planck data – I. The Perseus region as a test case

• Published in: Monthly notices of the Royal Astronomical Society 2015-07, Vol.451 (1), p.1056-1069
• Main Authors: Stanchev, Orlin, Veltchev, Todor V., Kauffmann, Jens, Donkov, Sava, Shetty, Rahul, Körtgen, Bastian, Klessen, Ralf S.
• Format: Article
• Language: English
• Subjects: Clouds; Computational fluid dynamics; Density; Diffusion; Invariants; Molecular clouds; Plasma; Probability density functions; Probability distribution; Space telescopes; Star & galaxy formation; Star maps; Turbulence
• ISSN: 0035-8711; 1365-2966
• DOI: 10.1093/mnras/stv998

We present an analysis of probability distribution functions (pdfs) of column density in different zones of the star-forming region Perseus and its diffuse environment based on the map of dust opacity at 353 GHz available from the Planck archive. The pdf shape can be fitted by a combination of a lognormal function and an extended power-law tail at high densities, in zones centred at the molecular cloud Perseus. A linear combination of several lognormals fits very well the pdf in rings surrounding the cloud or in zones of its diffuse neighbourhood. The slope of the mean-density scaling law 〈ρ 〉 L ∝L α is steep (α = −1.93) in the former case and rather shallow (α = −0.77 ± 0.11) in the rings delineated around the cloud. We interpret these findings as signatures of two distinct physical regimes: (i) a gravoturbulent one which is characterized by nearly linear scaling of mass and practical lack of velocity scaling; and (ii) a predominantly turbulent one which is best described by steep velocity scaling and by invariant for compressible turbulence $\langle \rho \rangle _L u_L^3/L$ , describing a scale-independent flux of the kinetic energy per unit volume through turbulent cascade. The gravoturbulent spatial domain can be identified with the molecular cloud Perseus while a relatively sharp transition to predominantly turbulent regime occurs in its vicinity.