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Supersonic turbulence plays a pivotal role during the formation of molecular clouds and stars in galaxies. However, little is known about how the fraction of compressive and solenoidal modes in the velocity field evolves over time and how…

Astrophysics of Galaxies · Physics 2020-07-29 Bastian Körtgen

Stars form by gravoturbulent fragmentation of interstellar gas clouds. The supersonic turbulence ubiquitously observed in Galactic molecular gas generates strong density fluctuations with gravity taking over in the densest and most massive…

Super-sonic turbulence fragments molecular clouds (MC) into a very complex density field with density contrasts of several orders of magnitude. A fraction of the gas is locked into dense and gravitationally bound cores, which collapse as…

Astrophysics · Physics 2007-05-23 Paolo Padoan , AAke Nordlund , Ornolfur Einar Rognvaldsson , Alyssa Goodman

We review current understanding of star formation, outlining an overall theoretical framework and the observations that motivate it. A conception of star formation has emerged in which turbulence plays a dual role, both creating…

Astrophysics · Physics 2008-11-26 Christopher F. McKee , Eve C. Ostriker

A fundamental property of molecular clouds is that they are turbulent, but how this turbulence is generated and maintained is unknown. One possibility is that stars forming within the cloud regenerate turbulence via their outflows, winds…

Solar and Stellar Astrophysics · Physics 2018-10-17 Stella S. R. Offner , Yue Liu

A large fraction of the gas in the Galaxy is cold, dense, and molecular. If all this gas collapsed under the influence of gravity and formed stars in a local free-fall time, the star formation rate in the Galaxy would exceed that observed…

Astrophysics of Galaxies · Physics 2017-10-04 Mordecai-Mark Mac Low , Andreas Burkert , Juan C. Ibáñez-Mejía

An overview is presented of the main properties of the interstellar medium. Evidence is summarized that the interstellar medium is highly turbulent, driven on different length scales by various energetic processes. Large-scale turbulence…

Astrophysics · Physics 2009-11-11 Andreas Burkert

We present preliminary numerical evidence that the physical conditions in high-mass star forming regions can arise from global gravitational infall, with the velocity dispersions being caused primarily by infall motions rather than random…

We review the main results from recent numerical simulations of turbulent fragmentation and star formation. Specifically, we discuss the observed scaling relationships, the ``quiescent'' (subsonic) nature of many star-forming cores, their…

Astrophysics · Physics 2008-11-26 Javier Ballesteros-Paredes

[Abridged] Theoretical and numerical studies of star formation have shown that magnetic field (B) has a strong influence on both disk formation and fragmentation; even a relatively low B can prevent these processes. However, very few…

Solar and Stellar Astrophysics · Physics 2015-06-12 Marc Joos , Patrick Hennebelle , Andrea Ciardi , Sebastien Fromang

The nature of turbulence in molecular clouds is one of the key parameters that control star formation efficiency: compressive motions, as opposed to solenoidal motions, can trigger the collapse of cores, or mark the expansion of Hii…

We revisit the origin of Larson's scaling relations, which describe the structure and kinematics of molecular clouds, based on recent observations and large-scale simulations of supersonic turbulence. Using dimensional analysis, we first…

Astrophysics of Galaxies · Physics 2012-02-17 Alexei G. Kritsuk , Michael L. Norman

Observational evidence from local star-forming regions mandates that star formation occurs shortly after, or even during, molecular cloud formation. Models of the formation of molecular clouds in large-scale converging flows have identified…

Astrophysics of Galaxies · Physics 2015-05-27 Jonathan Carroll-Nellenback , Adam Frank , Fabian Heitsch

The mass and size distributions are the key characteristics of any astrophysical objects, including the densest clumps comprising the cold phase of multiphase environments. In our recent papers, we showed how individual clouds of various…

Astrophysics of Galaxies · Physics 2019-05-01 Tim Waters , Daniel Proga

Star clusters are known to be formed in turbulent molecular clouds. How turbulence is driven in molecular clouds and what effect this has on star formation is still unclear. We compare a simulation setup with turbulent driving everywhere in…

Astrophysics of Galaxies · Physics 2022-09-28 Jamie D. Smith , James E. Dale , Sarah E. Jaffa , Martin G. H. Krause

The primordial clouds in the mini-halos hatch the first generation stars of the universe, which play a crucial role in cosmic evolution. In this paper, we investigate how the turbulence impacts the structure of primordial star-forming…

Astrophysics of Galaxies · Physics 2024-03-14 Ching-Yao Tang , Ke-Jung Chen

Molecular clouds have broad linewidths suggesting turbulent supersonic motions in the clouds. These motions are usually invoked to explain why molecular clouds take much longer than a free-fall time to form stars. It has classically been…

Astrophysics · Physics 2011-02-11 Mordecai-Mark Mac Low

Motivated by recent observational searches of sub-structure in starless molecular cloud cores, we investigate the evolution of density perturbations on scales smaller than the Jeans length embedded in contracting isothermal clouds, adopting…

Solar and Stellar Astrophysics · Physics 2017-12-20 C. Toci , D. Galli , A. Verdini , L. Del Zanna , S. Landi

The interaction of turbulence, magnetic fields, self-gravity, and stellar feedback within molecular clouds is crucial for understanding star formation. We study the effects of self-gravity and outflow feedback on the properties of the…

Astrophysics of Galaxies · Physics 2022-04-25 Yue Hu , Christoph Federrath , Siyao Xu , Sajay Sunny Mathew

MHD turbulence plays a central role in the physics of star-forming molecular clouds and the interstellar medium. I here show that MHD turbulence in molecular clouds must be driven to account for the observed supersonic motions in the…

Astrophysics · Physics 2007-05-23 Mordecai-Mark Mac Low