English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Tools annual

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools monthly

Global: Zendy Plus monthly

Presents the access of premium content as premium feature

Premium Content

Global: Zendy Plus annual

Global: Zendy Free Plan

(Modified) The scaling of velocity fluctuation, dv, as a function of spatialscale L in molecular clouds can be measured from size-linewidth relations,principal component analysis, or line centroid variation. Differing values ofthe power law index of the scaling relation dv = L^(g3D) in 3D are given bythese different methods: the first two give g3D=0.5, while line centroidanalysis gives g3D=0. This discrepancy has previously not been fullyappreciated, as the variation of projected velocity line centroid fluctuations(dv_{lc} = L^(g2D)) is indeed described, in 2D, by g2D=0.5. However, ifprojection smoothing is accounted for, this implies that g3D=0. We suggest thata resolution of this discrepancy can be achieved by accounting for the effectof density inhomogeneity on the observed g2D obtained from velocity linecentroid analysis. Numerical simulations of compressible turbulence are used toshow that the effect of density inhomogeneity statistically reverses the effectof projection smoothing in the case of driven turbulence so that velocity linecentroid analysis does indeed predict that g2D=g3D=0.5. Using our numericalresults we can restore consistency between line centroid analysis, principalcomponent analysis and size-linewidth relations, and we derive g3D=0.5,corresponding to shock-dominated (Burgers) turbulence. We find that thisconsistency requires that molecular clouds are continually driven on largescales or are only recently formed.Comment: 28 pages total, 20 figures, accepted for publication in Ap

Modification of Projected Velocity Power Spectra by Density Inhomogeneities in Compressible Supersonic Turbulence