High-fidelity view of the structure and fragmentation of the high-mass, filamentary IRDC G11.11-0.12

作者：Kainulainen J^*; Ragan S E; Henning T; Stutz A

来源：Astronomy & Astrophysics, 2013, 557: A120.

DOI：10.1051/0004-6361/201321760

• ISM: clouds
• ISM: structure
• stars: formation
• dust, extinction

Star formation in molecular clouds is intimately linked to their internal mass distribution. We present an unprecedentedly detailed analysis of the column density structure of a high-mass, filamentary molecular cloud, namely IRDC G11.11-0.12 (G11). We use two novel column density mapping techniques: high-resolution (FWHM = 2 '', or similar to 0.035 pc) dust extinction mapping in near-and mid-infrared, and dust emission mapping with the Herschel satellite. These two completely independent techniques yield a strikingly good agreement, highlighting their complementarity and robustness. We first analyze the dense gas mass fraction and linear mass density of G11. We show that G11 has a top heavy mass distribution and has a linear mass density (M-l similar to 600 M-circle dot pc(-1)) that greatly exceeds the critical value of a self-gravitating, non-turbulent cylinder. These properties make G11 analogous to the Orion A cloud, despite its low star-forming activity. This suggests that the amount of dense gas in molecular clouds is more closely connected to environmental parameters or global processes than to the star-forming efficiency of the cloud. We then examine hierarchical fragmentation in G11 over a wide range of size-scales and densities. We show that at scales 0.5 pc greater than or similar to l greater than or similar to 8 pc, the fragmentation of G11 is in agreement with that of a self-gravitating cylinder. At scales smaller than l less than or similar to 0.5 pc, the results agree better with spherical Jeans' fragmentation. One possible explanation for the change in fragmentation characteristics is the size-scale-dependent collapse time-scale that results from the finite size of real molecular clouds: at scales l less than or similar to 0.5 pc, fragmentation becomes sufficiently rapid to be unaffected by global instabilities.

• 出版日期2013-9