This is James Wadsley's gallery of images of the astrophysical simulations we are running at McMaster University using the computing resources of the SHARCNET collaboration ( Some simulations shown were run elsewhere.

The software we are using is the parallel SPH tree-code "Gasoline" developed at the University of Washington, "N-body Shop" by James Wadsley, Joachim Stadel and Tom Quinn. This paper describes Gasoline.

Dwarf Galaxies and the Destruction of Dark Matter Cusps
As recently presented in Stellar Feedback in Dwarf Galaxy Formation Sergey Mashchenko, James Wadsley, H. M. P. Couchman (2008, Science, 319, 174), we have demonstrated that star formation is particularly effective at removing dark matter cusps in dwarf galaxies. All that is required is clustered star formation and reasonable levels of supernova feedback. We expect the dark matter cores to persist as galaxies merge so that once cusps are removed they never reform. In addition, this is a first demonstration of clustered star formation in a cosmological dwarf galaxy. The clusters closely resemble globular clusters as can be seen in the image and animation below.

Divx/avi Animation (40 MB)

Star Formation in a low mass Molecular Cloud
Nicholas Petitclerc, James Wadsley, Alison Sills
The collapse of a fairly spherical, turbulent 50 solar mass molecular cloud is modelled. As the collapse proceeds the gas progresses from nearly constant temperatures (where cooling is efficient) to nearly adiabatic evolution. At high densities unstable gas clumps are replaced by sink particles which model young accreting stars.

Click here for the full movie: AVI Movie . Below is an animated gif of a late stage of the simulation.

Young star (proto-stellar disk) collisions and fragmentation to form Brown Dwarfs :
Visualizations of simulations completed by Sijing Shen for her Masters Thesis (May 2006)
Click for MPEG Movie (5.9 MB) Click here for a detailed description of the movies, images and associated research.

START: Two proto-stellar disks


END: Brown Dwarfs in orbit
(Binary is bottom, centre)

Brown Dwarf Binary
(Zoom in, edge and face-on)
Note: click on above images for full size

Gas surface density
[Animation: ON , OFF, new window]
Simulated Optical Image
[Animation: ON, OFF, new window]
Simulated Infrared Image

Galaxy Formation: Isolated Galaxy Movie

Fabio Governato, James Wadsley 2005
This is an isolated galaxy test run. The movie frames use realistic colours and brightnesses for the stars that fade rapidly from blue to red over time. The greenish material represents the gas from which the stars are being formed.

Gas Giant Planet Formation

"Forming Giant Planets via Fragmentation of Protoplanetary Disks"
Lucio Mayer, Tom Quinn, James Wadsley and Joachim Stadel
Published in SCIENCE, appeared on Nov 29th, 2002.

These Gasoline simulations are the first to demonstrate that framentation of a gas disk around a young star can produce giant gas planets. The planets have properties similar to the observed large extra-solar planets. Please read the science article for full details or see the McMaster press release . The simulations were performed at the Pittsburgh Supercomputing Center and CINECA (Italy).
Four panels [Click image to see full size] showing the evolution of a disk of gas around a young star. In the top two panels the disk is not cold or heavy enough to fragment (proving our simuation method is correct [Q=1.75]). In the lower two panels the disk is marginally unstable to fragmentation [Q=1.4]. The left two panels are after 160 yr and the right two after 350 yr.

Click here for the MOVIE . This MPEG movie (1.2 MB) covers the evolution from 120 to 300 years in a case that is marginally unstable. Several Jupiter-like planets are formed.

The image [click it for full size] shows the disk at 350 years.

Galaxy collisions

This is a standard equal mass galaxy merger from Mihos and Hernquist (1996, ApJ) with 100K particles (stars and dark matter). This is similar to the upcoming Andromeda - Milky Way collision.

Shorter Movie, 2.8 MB Longer Movie, 30 MB

Cosmological Hydrodynamical Simulations

James W. Wadsley (McMaster University)
Marcelo I. Ruetalo (CITA)
J. Richard Bond (CITA)
Carlo R. Contaldi (CITA)
Hugh M. P. Couchman (McMaster University)
Joachim Stadel (University of Victoria)
Thomas R. Quinn (University of Washington, Seattle)
Michael D. Gladders (University of Toronto)

The 270 million particle simulation shown was presented by James Wadsley at the Canadian Astronomical Society (CASCA) meeting 2002 in Penticton, BC (May 11-14).

270 Million Particle Poster

Poster image 3600x3600 GIF, 16 MB. Poster image 600x600 GIF, 0.3 MB. Full Poster with caption, title PDF, 33 MB

The image shows gas density on a periodically extended 2.8 by 2.6 billion light year sheet, 290 million light years thick (displaying each part of the volume once). Each bright point is a large galaxy or group of galaxies evolved within a Lambda cold dark matter cosmology to the current time. We are studying the galaxy clusters making up the beautiful large scale structures through their predicted X-rays, gravitational lensing and Sunyaev-Zel'dovich effect.

The simulation was run by James Wadsley at McMaster University on Idra, a 112 processor Compaq AlphaServer acquired through SHARCNET. It was run using the Gasoline parallel SPH and N-Body code (Wadsley, Stadel and Quinn) with 512 cubed 17 billion solar mass dark matter particles and 512 cubed gas particles. Gasoline has sustained over 50 GFLOPS on Idra. The Sharc-Net consortium is an ORDCF/CFI project to boost high performance parallel computing in Ontario

Movie Details

The movies are all perspective views. The viewable area has a depth of 200 Mpc and is 200 Mpc x 200 Mpc at the middle depth of the view. In the later part of each movie the particles are periodically replicated to give a continuous universe view.

The movies may play more cleanly if you download the .mpg first and then play them (eg. mpeg_play). They look best at 16 bpp. I suggest trying a framerate of 10 fps and double size if your screen height is 768 or more pixels (eg. mpeg_play -framerate 10 -dither color2).

270 Million particles: 5123 Gas 5123 Dark

This is a large chunk of the universe 400 Mpc (1.3 Billion Light years) on a side, resolving clusters of galaxies and other large scale structures. For comparison the observable universe is 26 Billion Light years across. The large box makes it possible to have rarer events occur in the box because larger structures (waves) correlated with the rarest events may be resolved. The largest relaxed objects in the simulation are around a million billion (1015) Solar masses, each one resolved with 100,000 simulation particles.

The simulation was performed by James Wadsley on Idra, the McMaster SHARCNET 114 Processor Compaq Alphaserver, and used 80 GB of memory and 100,000 node hours of CPU (11 years of computing for a single machine).

Mosaic of Entire Box at Redshift 0 (Current Time) (contiguous 400x400x40 Mpc slices) showing Density
Movie of Gas Density (98 MB Mpeg)
Movie of Gas Temperature (94 MB Mpeg)
Movie of Total Matter Density (high contours) (85 MB Mpeg)

4 Million particles: 1283 Gas 1283 Dark

This is a smaller chunk of the universe 200 Mpc (650 Million Light years) on a side, suitable for resolving clusters of galaxies and other large scale structure.

Movie of Gas Density (86 MB Mpeg)
Movie of Gas Temperature (106 MB Mpeg)

This Website is maintained by James Wadsley , Associate Professor in the McMaster University Physics and Astronomy Department.