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Observations find a median star formation efficiency per free-fall time in Milky Way Giant Molecular Clouds (GMCs) on the order of $\epsilon_{\rm ff}\sim 1\%$ with dispersions of $\sim0.5\,{\rm dex}$. The origin of this scatter in…

Astrophysics of Galaxies · Physics 2019-05-08 Kearn Grisdale , Oscar Agertz , Florent Renaud , Alessandro B. Romeo , Julien Devriendt , Adrianne Slyz

Galactic star formation scaling relations show increased scatter from kpc to sub-kpc scales. Investigating this scatter may hold important clues to how the star formation process evolves in time and space. Here, we combine different…

Astrophysics of Galaxies · Physics 2017-06-14 Bram B. Ochsendorf , Margaret Meixner , Julia Roman-Duval , Mubdi Rahman , Neal J. Evans

Molecular clouds are supported by turbulence and magnetic fields, but quantifying their influence on cloud lifecycle and star formation efficiency (SFE) remains an open question. We perform radiation MHD simulations of star-forming giant…

Astrophysics of Galaxies · Physics 2021-05-05 Jeong-Gyu Kim , Eve C. Ostriker , Nina Filippova

It has been known for more than 30 years that star formation in giant molecular clouds (GMCs) is slow, in the sense that only ~1% of the gas forms stars every free-fall time. This result is entirely independent of any particular model of…

Astrophysics · Physics 2008-11-26 Mark R. Krumholz , Jonathan C. Tan

We use a sample of the 13 most luminous WMAP Galactic free-free sources, responsible for 33% of the free- free emission of the Milky Way, to investigate star formation. The sample contains 40 star forming complexes; we combine this sample…

Astrophysics of Galaxies · Physics 2015-05-19 Norman Murray

We present the results of a numerical simulation in which star formation proceeds from an initially unbound molecular cloud core. The turbulent motions, which dominate the dynamics, dissipate in shocks leaving a quiescent region which…

Astrophysics · Physics 2009-11-10 Paul C. Clark , Ian A. Bonnell

Energetic feedback from star clusters plays a pivotal role in shaping the dynamical evolution of giant molecular clouds (GMCs). To study the effects of stellar feedback on the star formation efficiency of the clouds and the dynamical…

Astrophysics of Galaxies · Physics 2019-05-29 Hui Li , Mark Vogelsberger , Federico Marinacci , Oleg Y. Gnedin

Multiple mechanisms are proposed for the formation of giant molecular clouds (GMCs), from gravitational free-fall caused by self-gravity to stellar feedback-driven gas compression. Both the galactic environment and galaxy conditions could…

We present a detailed study of the evolution of GMCs in a galactic disc simulation. We follow individual GMCs (defined in our simulations by a total column density criterion), including their level of star formation, from their formation to…

Astrophysics of Galaxies · Physics 2015-06-15 C. L. Dobbs , J. E. Pringle

Giant molecular clouds (GMCs) are well-studied in the local Universe, however, exactly how their properties vary during galaxy evolution is poorly understood due to challenging resolution requirements, both observational and computational.…

We present a study of a star formation prescription in which star formation efficiency depends on local gas density and turbulent velocity dispersion, as suggested by direct simulations of SF in turbulent giant molecular clouds (GMCs). We…

Astrophysics of Galaxies · Physics 2017-08-22 Vadim A. Semenov , Andrey V. Kravtsov , Nickolay Y. Gnedin

It remains a major challenge to derive a theory of cloud-scale ($\lesssim100$ pc) star formation and feedback, describing how galaxies convert gas into stars as a function of the galactic environment. Progress has been hampered by a lack of…

We describe an overall picture of galactic-scale star formation. Recent high-resolution magneto-hydrodynamical simulations of two-fluid dynamics with cooling/heating and thermal conduction have shown that the formation of molecular clouds…

Astrophysics of Galaxies · Physics 2015-07-29 Shu-ichiro Inutsuka , Tsuyoshi Inoue , Kazunari Iwasaki , Takashi Hosokawa

The physics of star formation and the deposition of mass, momentum, and energy into the interstellar medium by massive stars (`feedback') are the main uncertainties in modern cosmological simulations of galaxy formation and evolution. These…

The processes of star formation and feedback, regulating the cycle of matter between gas and stars on the scales of giant molecular clouds (GMCs; $\sim$100pc), play a major role in governing galaxy evolution. Measuring the time-scales of…

We investigate the formation and evolution of giant molecular clouds (GMCs) in a Milky-Way-like disk galaxy with a flat rotation curve. We perform a series of 3D adaptive mesh refinement (AMR) numerical simulations that follow both the…

Astrophysics · Physics 2009-07-22 Elizabeth J. Tasker , Jonathan C. Tan

We estimate the star formation efficiency per gravitational free fall time, $\epsilon_{\rm ff}$, from observations of nearby galaxies with resolution matched to the typical size of a Giant Molecular Cloud. This quantity, $\epsilon_{\rm…

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,…

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

All stars are born in molecular clouds, and most in giant molecular clouds (GMCs), which thus set the star formation activity of galaxies. We first review their observed properties, including measures of mass surface density, Sigma, and…

Astrophysics of Galaxies · Physics 2015-06-12 Jonathan C. Tan , Suzanne N. Shaske , Sven Van Loo
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