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The Formation of Clusters of Stars and Brown Dwarfs

Matthew R. Bate

Copyright and other information can be found at the bottom of this page.

Since 2001, I have been performing some of the world's most complex computer simulations of star formation. The first calculation was of a relatively small 50 solar-mass star-forming cloud. It was purely hydrodynamical and performed in collaboration with Ian Bonnell (University of St Andrews) and Volker Bromm (Harvard-Smithsonian Center for Astrophysics) and was press released in April 2002. This was followed by 3 more hydrodynamical calculations investigating the effects of the star formation process on variations of the initial conditions and heating of the gas. The hydrodynamical simulations have culminated in a large-scale simulation of a 500 solar-mass cloud that formed more than 1250 stars and brown dwarfs and enabled the statistical properties of stars to be compared in detail with observations.

More recently, I have been including radiative transfer and magnetic fields into the simulations. The effects of these processes on the star formation process have been investigated by repeating the original 50 solar-mass calculations (below), but including radiative transfer and magnetic fields. The work with magnetic fields was done with Daniel Price and animations can be found at his website.

My most recent star cluster calculations are of 500 solar-mass clouds and includes radiative feedback. For calculations with different metallicities have been performed to date. Each produces 170-198 stars and brown dwarfs, including dozens of multiple stellar systems, the properties of which are in good agreement with observed stellar systems.

Radiation Hydrodynamical Simulations (2009-present)

My largest radiation hydrodynamical star cluster formation simulations to date are of 500 solar-mass molecular clouds which collapse to produce a stars clusters containing 170-198 stars and brown dwarfs. Animations of these simulations showing both the column density and temperature were created. Click on the images below for more detail and to view the animations.

Solar metallicity
Bate (2012)

Two smaller (50 solar mass) radiation hydrodynamical calculations have also been performed (Bate 2009b). They are re-runs of Calculations 1 and 2 (listed below), but include the radiative feedback from the protostars. This heats the surrounding gas and changes the star formation process. In particular, fewer objects are formed and the ratio of stars to brown dwarfs is increased, in better agreement with observations.

Hydrodynamical Simulations (2001-2009)

The largest hydrodynamical star cluster formation simulation was that of a 500 solar-mass molecular cloud which collapsed to produce a star cluster containing more than 1250 stars and brown dwarfs (Bate 2009a). Animations of this simulation were created in both 2-D and 3-D. Click on the images below for more detail and to view the animations.

Four hydrodynamical calculations of 50 solar-mass molecular clouds were performed.

  • Calculation 1: Original calculation: Mean thermal Jeans mass 1 solar mass, minimum object mass ~3 Jupiter masses. (Bate, Bonnell & Bromm 2002a,b, 2003)

  • Calculation 2: Denser molecular cloud: Mean thermal Jeans mass 1/3 solar mass, minimum object mass ~3 Jupiter masses. (Bate & Bonnell 2005)

  • Calculation 3: Low Metallicity cloud: Mean thermal Jeans mass 1 solar mass, minimum object mass ~9 Jupiter masses. (Bate 2005)

  • Calculation 4: Cloud with different initial turbulent power spectrum: Mean thermal Jeans mass 1 solar mass, minimum object mass ~3 Jupiter masses, P(k)~k^{-6}. (Bate 2009c)

These test the dependence of star formation on the initial conditions in molecular clouds. Animations of all four calculations are available. Click on the images below for animations and detailed information.

Original Calculation   Original Calculation vs Denser Cloud   Denser Cloud  
Original Calculation vs Low Metallicity   Original Calculation vs Different Power Spectrum    
Low Metallicity Cloud   Low Metallicity vs Different Power Spectrum   Different Turbulent Power Spectrum  

About these pages

Many of the theoretical calculations I conduct during my research into star and planet formation result in animations. New animations will be added at the top of the page with the dates that they were added.

Copyright: Unless otherwise stated, all of the material on this site is the property of Matthew Bate. Any of my pictures and animations may be used freely for non-profit purposes (such as during scientific talks) as long as appropriate credit is given wherever they appear. Permission must be obtained from me before using them for any other purpose (e.g. pictures for publication in books).

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