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It is speculated that the high star-formation efficiency observed in spiral-arm molecular clouds is linked to the prevalence of compressive (curl-free) turbulent modes, while the shear-driven solenoidal (divergence-free) modes appear to be…

Astrophysics of Galaxies · Physics 2022-07-20 Raffaele Rani , Toby J. T. Moore , David J. Eden , Andrew J. Rigby

Molecular clouds are to a great extent influenced by turbulent motions in the gas. Numerical and observational studies indicate that the star formation rate and efficiency crucially depend on the mixture of solenoidal and compressive modes…

Astrophysics of Galaxies · Physics 2017-10-11 Bastian Körtgen , Christoph Federrath , Robi Banerjee

The efficiency of star formation, defined as the ratio of the stellar to total (gas and stellar) mass, is observed to vary from a few percent in regions of dispersed star formation to about a third in cluster-forming cores. This difference…

Astrophysics · Physics 2009-11-10 Fumitaka Nakamura , Zhi-Yun Li

We summarize the current status of the turbulent model of star formation in turbulent molecular clouds. In this model, clouds, clumps and cores form a hierarchy of nested density fluctuations caused by the turbulence, and either collapse or…

Astrophysics · Physics 2007-05-23 Enrique Vazquez-Semadeni

Star formation is inefficient. Recent advances in numerical simulations and theoretical models of molecular clouds show that the combined effects of interstellar turbulence, magnetic fields and stellar feedback can explain the low…

Solar and Stellar Astrophysics · Physics 2020-02-12 Christoph Federrath

We determine the physical properties and turbulence driving mode of molecular clouds formed in numerical simulations of a Milky Way-type disc galaxy with parsec-scale resolution. The clouds form through gravitational fragmentation of the…

Astrophysics of Galaxies · Physics 2017-05-31 Keitaro Jin , Diane M. Salim , Christoph Federrath , Elizabeth J. Tasker , Asao Habe , Jouni T. Kainulainen

Star formation is intimately linked to the dynamical evolution of molecular clouds. Turbulent fragmentation determines where and when protostellar cores form, and how they contract and grow in mass via accretion from the surrounding cloud…

Astrophysics · Physics 2007-05-23 Ralf Klessen

We review recent advances in the analytical and numerical modeling of the star formation rate in molecular clouds and discuss the available observational constraints. We focus on molecular clouds as the fundamental star formation sites,…

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

Star formation is intimately linked to the dynamical evolution of molecular clouds. Turbulent fragmentation determines where and when protostellar cores form, and how they contract and grow in mass via accretion from the surrounding cloud…

Astrophysics · Physics 2007-05-23 Ralf Klessen

Supersonic flows in the interstellar medium (ISM) are believed to be a key driver of the molecular cloud formation and evolution. Among molecular clouds' properties, the ratio between the solenoidal and compressive modes of turbulence plays…

Astrophysics of Galaxies · Physics 2022-05-18 Masato I. N. Kobayashi , Tsuyoshi Inoue , Kengo Tomida , Kazunari Iwasaki , Hiroki Nakatsugawa

Molecular clouds are observed to be turbulent, but the origin of this turbulence is not well understood. As a result, there are two different approaches to simulating molecular clouds, one in which the turbulence is allowed to decay after…

Astrophysics · Physics 2009-11-13 Stella S. R. Offner , Richard I. Klein , Christopher F. McKee

We review the properties of turbulent molecular clouds (MCs), focusing on the physical processes that influence star formation (SF). MC formation appears to occur during large-scale compression of the diffuse ISM driven by supernovae,…

Astrophysics · Physics 2007-05-23 J. Ballesteros-Paredes , R. S. Klessen , M. -M. Mac Low , E. Vazquez-Semadeni

Observed molecular clouds often appear to have very low star formation efficiencies and lifetimes an order of magnitude longer than their free-fall times. Their support is attributed to the random supersonic motions observed in them. We…

Astrophysics · Physics 2010-10-28 Ralf S. Klessen , Fabian Heitsch , Mordecai-Mark Mac Low

Filaments are a key step on the path that leads from molecular clouds to star formation. However, their characteristics are heavily debated, and the exact processes that lead to their formation and fragmentation into dense cores still…

In this study, we investigate the shapes of starless and protostellar cores using hydrodynamic, self-gravitating adaptive mesh refinement simulations of turbulent molecular clouds. We simulate observations of these cores in dust emission,…

Astrophysics · Physics 2011-02-11 S. S. R. Offner , M. R. Krumholz

Star formation is primarily controlled by the interplay between gravity, turbulence, and magnetic fields. However, the turbulence and magnetic fields in molecular clouds near the Galactic Center may differ substantially from spiral-arm…

Stars form in molecular clouds in the interstellar medium (ISM) with a turbulent kinematic state. Newborn stars therefore should retain the turbulent kinematics of their natal clouds. Gaia DR2 and APOGEE-2 surveys in combination provide…

Astrophysics of Galaxies · Physics 2021-02-05 Trung Ha , Yuan Li , Siyao Xu , Marina Kounkel , Hui Li

Star formation in the Galactic disc is primarily controlled by gravity, turbulence, and magnetic fields. It is not clear that this also applies to star formation near the Galactic Centre. Here we determine the turbulence and star formation…

The compressibility of molecular cloud (MC) turbulence plays a crucial role in star formation models, because it controls the amplitude and distribution of density fluctuations. The relation between the compressive ratio (the ratio of…

Astrophysics of Galaxies · Physics 2016-07-06 Liubin Pan , Paolo Padoan , Troels Haugbolle , Aake Nordlund
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