The Birth of Molecular Clouds: Formation of Atomic Precursors in Colliding Flows

By F. Heitsch, A. Slyz, J. Devriendt, L. Hartmann, A. Burkert. 2006

165 citations recorded by the source corpus.

Molecular cloud complexes (MCCs) are highly structured and "turbulent." Observational evidence suggests that MCCs are dynamically dominated systems, rather than quasi-equilibrium entities. The observed structure is more likely a consequence of the formation process than something that is imprinted after the formation of the MCC. Converging flows provide a natural mechanism to generate MCC structure. We present a detailed numerical analysis of this scenario. Our study addresses the evolution of an MCC from its birth in colliding atomic hydrogen flows up until the point when H2 may begin to form. A combination of dynamical and thermal instabilities breaks up coherent flows efficiently, seeding the small-scale nonlinear density perturbations necessary for local gravitational collapse and thus allowing (close to) instantaneous star formation. Many observed properties of MCCs come as a natural consequence of this formation scenario. Since converging flows are omnipresent in the ISM, we discuss the general applicability of this mechanism, from local star formation regions to galaxy mergers.

Subfields: Astronomy and Astrophysics, Atomic and Molecular Physics, and Optics

View Paper: https://www.semanticscholar.org/paper/01699cd47bb56b5cb2c05ff71610f2f4b2c125ac

How researchers see this paper

The researchers whose trusted networks rank it highest, strongest advocate first. Every researcher gets a different order.

In Astronomy and Astrophysics

In Atomic and Molecular Physics, and Optics

Citations in the corpus

Global hierarchical collapse in molecular clouds. Towards a comprehensive scenario (2019, background): “…(NTSI; Vishniac 1994), which, aided by the thermal, Kelvin-Helmholz and Rayleigh-Taylor instabilities, causes significantly nonlinear (large-amplitude) density fluctuations (Koyama & Inutsuka 2002; Heitsch et al. 2006; Vázquez-Semadeni et al. 2006; Banerjee et al. 2009; Wareing et al. 2019).”
Gravity or turbulence? II. Evolving column density PDFs in molecular clouds (2011, background): “…the same cloud at different evolutionary times appears as if it were different kind of objects: at earlier times, the compressed layer could be classified as a diffuse H I cloud, with low column densities and thus, very little CO content (see Heitsch et al. 2006; Vázquez-Semadeni et al. 2006).”
PHYSICAL PROPERTIES OF MOLECULAR CLOUDS FOR THE ENTIRE MILKY WAY DISK (2016, background): “In this scenario, molecular clouds are dynamical structures, and stars form early in the densest small-scale substructures of the cloud (Heitsch et al. 2006), solving the problem of the origin of turbulent energy; the initial collapse drives turbulence, which decays, but not before the cloud is…”
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,…”
A NEW JEANS RESOLUTION CRITERION FOR (M)HD SIMULATIONS OF SELF-GRAVITATING GAS: APPLICATION TO MAGNETIC FIELD AMPLIFICATION BY GRAVITY-DRIVEN TURBULENCE (2011, background): “…massive star clusters (Mac Low & Klessen 2004; Schneider et al. 2010), and the galactic spiral shock, producing large-scale converging flows (Vishniac 1994; Walder & Folini 1996; VázquezSemadeni et al. 2006; Heitsch et al. 2006; Hennebelle et al. 2008; Banerjee et al. 2009; Folini et al. 2010).”
Numerical simulations of compressively driven interstellar turbulence. I. Isothermal gas (2008, methodology): “Typical examples for the first approach are the simulations of colliding flows by Heitsch et al. (2006), Vázquez-Semadeni et al. (2007) and Hennebelle & Audit (2007).”
Cooling, Gravity, and Geometry: Flow-driven Massive Core Formation (2007, methodology): “Several numerical studies relevant to this problem have now been undertaken (see the discussions of the literature in Heitsch et al. 2006 and Vázquez-Semadeni et al. 2007).”
Planck intermediate results: XXXV. Probing the role of the magnetic field in the formation of structure in molecular clouds (2015, unknown): “…as isolated entities but as the result of an accumulation of gas by large-scale ﬂows (Ballesteros-Paredes et al. 1999; Hartmann et al. 2001; Koyama & Inutsuka 2002; Audit & Hennebelle 2005; Heitsch et al. 2006), the material swept up by colliding ﬂows may eventually form a self-gravitating cloud.”
Comparing the statistics of interstellar turbulence in simulations and observations - Solenoidal versus compressive turbulence forcing (2009, background): “5 http://www.ita.uni-heidelberg.de/ chfeder/videos.shtml?lang=en (e.g., Heitsch et al. 2006; Vázquez-Semadeni et al. 2006; Hennebelle et al. 2008; Banerjee et al. 2008) are more suitable for studying the boundary effects during the formation of molecular clouds.”
The exciting lives of giant molecular clouds (2013, background): “…formation times, there have been two main possibilities - either diffuse gas is collected together in a colliding flow (Audit & Hennebelle 2005; Heitsch et al. 2006; Vázquez-Semadeni et al. 2007, 2010; Inoue & Inutsuka 2012) on a Myr timescale, or gas is relatively dense prior to becoming a…”
Accretion-driven turbulence as universal process: galaxies, molecular clouds, and protostellar disks (2009, background): “…form at the stagnation points of large-scale convergent flows (e.g. Ballesteros-Paredes et al. 1999; Hartmann et al. 2001; Klessen et al. 2005; Heitsch et al. 2006b; Hennebelle et al. 2008; Banerjee et al. 2009), maybe triggered by spiral density waves or other global perturbations of the…”
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).”