Formation of Structure in Molecular Clouds: A Case Study

By F. Heitsch, A. Burkert, L. Hartmann, A. Slyz, J. Devriendt. 2005

154 citations recorded by the source corpus.

Molecular clouds (MCs) are highly structured and turbulent. Colliding gas streams of atomic hydrogen have been suggested as a possible source of MCs, imprinting the filamentary structure as a consequence of dynamical and thermal instabilities. We present a two-dimensional numerical analysis of MC formation via converging H I flows. Even with modest flow speeds and completely uniform inflows, nonlinear density perturbations arise as possible precursors of MCs. Thus, we suggest that MCs are inevitably formed with substantial structure, e.g., strong density and velocity fluctuations, which provide the initial conditions for subsequent gravitational collapse and star formation in a variety of Galactic and extragalactic environments.

Subfields: Astronomy and Astrophysics, Atmospheric Science, Fluid Flow and Transfer Processes

View Paper: https://www.semanticscholar.org/paper/8efebe5d7b6fb4b766f6ae2a96dc668283b24f56

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Citations in the corpus

Molecular Cloud Evolution. I. Molecular Cloud and Thin Cold Neutral Medium Sheet Formation (2005, background): “A preliminary study of the development of the turbulence in these circumstances has been recently presented by Heitsch et al. (2005), who also investigated the masses and possible self-gravitating nature of the clumps formed by the induced turbulence.”
DIRECT OBSERVATION OF A SHARP TRANSITION TO COHERENCE IN DENSE CORES (2010, background): “Shocks are predicted in models of core formation in supersonic flows (Padoan et al. 1997) and in models of colliding large-scale flows, e.g. Heitsch et al. (2005).”
Turbulent molecular clouds (2012, background): “…either by a converging flow of WNM (Walder & Folini 1998, Hennebelle & Pérault 1999, 2000, Sánchez–Salcedo et al. 2002, Audit & Hennebelle 2005, 2010, Heitsch et al. 2005, 2006, Vázquez–Semadeni et al. 2006, Hennebelle & Audit 2007), or by shocks propagating in the WNM (Koyama & Inutsuka 00,…”
Gravity or turbulence? II. Evolving column density PDFs in molecular clouds (2011, background): “As the streams collide, the compressed regions undergo a nonlinearly induced thermal instability, cooling down rapidly and becoming turbulent due to a combination of various instabilities (Heitsch et al. 2005, 2006; Vázquez-Semadeni et al. 2006).”
Global hierarchical collapse in molecular clouds. Towards a comprehensive scenario (2019, background): “…including cooling and self-gravity show that fragmentation clearly does occur (e.g., Koyama & Inutsuka 2002; Audit & Hennebelle 2005, 2010; Heitsch et al. 2005, 2008a,b; Vázquez-Semadeni et al. 2007, 2010, 2011; Heitsch & Hartmann 2008; Hennebelle et al. 2008; Banerjee et al. 2009;…”
From the warm magnetized atomic medium to molecular clouds (2008, background): “…atomic gas (e.g. Ballesteros-Paredes et al. 1999) with the active role of thermal instability (Hennebelle & Pérault 1999, Koyama & Inutsuka 2000, 2002, Audit & Hennebelle 2005, Heitsch et al. 2005, Vázquez-Semadeni Send offprint requests to: P. Hennebelle patrick.hennebelle@ens.fr et al. 2006).”
The Birth of Molecular Clouds: Formation of Atomic Precursors in Colliding Flows (2006, methodology): “This work extends our previous study (Heitsch et al. 2005), in dimensions (here, we present corresponding 3D models), in resolution and in scope of physical applications.”
Theory of Star Formation (2007, background): “One conception of GMCs is that they are dynamic, transient entities in which the turbulence is driven by large-scale colliding gas flows that create the cloud (e.g. Heitsch et al. 2005; Vázquez-Semadeni et al. 2006; BallesterosParedes et al. 2007).”
Physical Processes in the Interstellar Medium (2014, background): “If the flows initially consist of warm atomic hydrogen, then their collision can trigger a thermal instability, leading to the rapid production of a cloud of much denser, cooler gas (see e.g. Hennebelle & Pérault, 1999, 2000; Koyama & Inutsuka, 2002; Audit & Hennebelle, 2005; Heitsch et al., 2005; V”
Cooling, Gravity, and Geometry: Flow-driven Massive Core Formation (2007, methodology): “In an extension of our previous work (Heitsch et al. 2005, 2006) we presented three-dimensional models of molecular cloud formation in colliding flows including self-gravity.”
Clump morphology and evolution in MHD simulations of molecular cloud formation (2008, background): “This process also causes the newly formed dense gas to be turbulent, with a transonic velocity dispersion with respect to its own sound speed (Koyama & Inutsuka 2002; Heitsch et al. 2005; Vázquez-Semadeni et al. 2006; Hennebelle et al. 2008).”
KINEMATIC DISTANCES TO MOLECULAR CLOUDS IDENTIFIED IN THE GALACTIC RING SURVEY (2009, background): “Hydrodynamical processes (i.e., compression in shocks, in over-densities created by turbulence, in converging streams; Audit & Hennebelle 2005; Heitsch et al. 2005; VazquezSemadeni et al. 2006) also play a major role in the formation of molecular clouds.”
Gravity or turbulence? Velocity dispersion–size relation (2010, background): “…& Pérault 1999) with the result that the gas cools rapidly, producing a dense, cold, turbulent cloud (Walder & Folini 1998; Koyama & Inutsuka 2002; Heitsch et al. 2005, 2006; Vázquez-Semadeni et al. 2006) which soon becomes Jeans unstable (Vázquez-Semadeni et al. 2007; Heitsch et al. 2008).”
The Statistics of Supersonic Isothermal Turbulence (2007, background): “These coherent structures are transient and form in supersonic collisions of counter-propagating flow patches or “blobs” (Kritsuk & Norman 2004; Heitsch et al. 2005; Kritsuk et al. 2006).”
Accretion-driven turbulence as universal process: galaxies, molecular clouds, and protostellar disks (2009, unknown): “…at which accretion energy is converted into turbulent energy we resort to numerical simulations of converging flows (e.g. Audit & Hennebelle 2005; Heitsch et al. 2005, 2006a; Folini & Walder 2006; Vázquez-Semadeni et al. 2006, 2007; Hennebelle et al. 2008; Banerjee et al. 2009; Audit &…”