GMCs
Research
Research on Turbulent GMCs and the IMF
Dark star-forming regions within the Eagle Nebula. The majority of star formation occurs in dense turbulent clouds of molecular Hydrogen. These Giant Molecular Clouds (GMCs) set the stage for the formation of protostellar systems by the gravitational collapse of dense regions within the GMC that fragment into smaller core components that in turn condense into stars. Hence the natal environment, through the complex interplay of gravity, magnetic fields, and supersonic turbulence, is an important influence on star formation. Exactly how these mechanisms shape the final properties of stars both collectively and individually is poorly understood. Important questions include: What is the origin of the stellar Initial Mass Funtion (IMF)? How is the final mass of a star determined? What determines whether a core forms a single star, binary, or multiple system?



NGC 604, a giant H II region in the Triangulum Galaxy. There has been a wide body of observation comparing and cataloging the properties of dense cores and Young Stellar Objects (YSO) across diverse star formation sites. This evidence suggests that core properties are greatly influenced by their proximity to other YSO and cores, which may be intimately related to the generation and sustenance of supersonic turbulence. Current theoretical thinking connects the IMF to the large-scale turbulence within a GMC. In this picture, the distribution of densities generated within a turbulent medium naturally gives rise to a power-law IMF similar to what is observed at the high end, and a substellar IMF which depends on the degree of turbulence of the parent region. Observation shows that the IMF of stars and prestellar cores are virtually identical, and so study of the initial conditions, properties, and evolution of prestellar cores is vital to answer the above questions.



The image below shows the log column density from a turbulent molecular cloud simulation. The panels show, from left to right, the full simulation, a filament forming cores, and a protostellar disk. Velocity vectors overlay the third panel.

Log column density of a turbulent molecular cloud simulation. The panels show, from left to right, the full simulation, a filamet forming cores, and a protostellar disk.

The image below depicts a density volume rendering of a magneto-hydrodynamic simulation showing the gas filaments formed in an infrared dark cloud (IRDC) 800,000 years after the highly supersonically turbulent region began gravitational collapse. The extent of the main filament is about 4.5 parsecs in length and equivalent to 660 solar masses. The highest density fragments in the filament (red) show regions where molecular cloud cores are forming which upon further gravitational collapse form low mass and high mass stars.

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To see the high resolution (1600x1200) version of the animation, click here. Due to the large size of the file, the animation is best seen after downloaded and plays locally.

An animation of density volume rendering of a magneto-hydrodynamic simulation showing gas filaments formed in an infrared dark cloud (IRDC) 5 parsecs in size, 800,000 years after the turbulent region began gravitational collapse is created by Tim Sandstrom (NASA visual team). A rotation around the IRDC zooms in on the main filament 4.5 parsecs in length showing a dense molecular core of 0.1 parsec size. Continued simulation of this region shows further collapse, filamentation, protostellar outflows and the early stage formation of a high mass star.

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