The Formation of Clusters of Stars and Brown Dwarfs

Matthew R. Bate

Since 2001, I have been performing 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.

Radiation Hydrodynamical Simulations (2007-)

Two radiation hydrodynamical calculations have been completed so far. 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 (2001-2007)

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. 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.
Calculation 2: Denser molecular cloud: Mean thermal Jeans mass 1/3 solar mass, minimum object mass ~3 Jupiter masses.
Calculation 3: Low Metallicity cloud: Mean thermal Jeans mass 1 solar mass, minimum object mass ~9 Jupiter masses.
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}.

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).