2009/05/04 by P. Hily-Blant, Pierre Hily-Blant, Edith Falgarone +1 · 2 citations
Chemical Engineering · Engineering · Physics and Astronomy · #Advanced Combustion Engine Technologies #Astrophysics #Astrophysics and Star Formation Studies #Combustion and flame dynamics #Computational physics #Galaxy #Intermittency #Meteorology #Molecular cloud #Physics #Turbulence #Velocity dispersion #astro-ph.GA
paper · pdf · doi:10.1051/0004-6361/200912296
arxiv created 2009/05/04 · openalex publication_date 2009/05/19 · arxiv updated 2015/05/13 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
<i>Aims. <i/>Benefitting from the duality of turbulence (random versus coherent motions), we search for coherent structures in the turbulent velocity field of molecular clouds, anticipating their importance in cloud evolution.<i>Methods. <i/>We analyse a large map (40´ by 20´) obtained with the HERA multibeam receiver (IRAM-30 m telescope) in a high latitude cloud of the Polaris Flare at unprecedented spatial (11´´) and spectral (0.05 km s<sup>-1<sup/>) resolution for the <sup>12<sup/>(2–1) line.<i>Results. <i/>We find that two parsec-scale components of velocities differing by <i>∼<i/>2 km s<sup>-1<sup/>, share a narrow interface (<0.15 pc) that appears to be an elongated structure of intense velocity-shear, <i>∼<i/>15 to 30 km s<sup>-1<sup/> pc<sup>-1<sup/>. The locus of the extrema of line–centroid-velocity increments (E-CVI) in that field follows this intense-shear structure as well as that of the <sup>12<sup/>(2–1) high-velocity line wings. The tiny spatial overlap in projection of the two parsec-scale components implies that they are sheets of CO emission and that discontinuities in the gas properties (CO enrichment and/or increase in gas density) occur at the position of the intense velocity shear.<i>Conclusions. <i/>These results identify spatial and kinematic coherence on scales of between 0.03 pc and 1 pc. They confirm that the departure from Gaussianity of the probability density functions of E-CVIs is a powerful statistical tracer of the intermittency of turbulence. They provide support for a link between large-scale turbulence, its intermittent dissipation rate and low-mass dense core formation.