Below are some of the movies my collaborators and I have made over my scientific career. Many of the movies date back to over a decade ago, as my focus had been more numerical.
I love this movie, made by my collaborator Prof. Anson D'Aloisio for a study he led. It shows radiative transfer simulations of ionization fronts sweeping over a small region of the Universe. The heated gas then starts to violently relax, smoothing out small structures. Understanding this relaxation, which takes hundreds of millions of years, is important for understanding reionization.
1D simulation of collapse of a Gaussian perturbation. This collapse shows the predictions for the evolution of the overdensity in the linear Eulerian theory, the Zeldovich approximation (first order Lagrangian perturbation theory), 2nd order Eulerian perturbation theory, and the full nonlinear solution calculated using N-body methods. Zeldovich is exact until shell crossing in 1D and so performs very well (and is the infinite order limit of the Eulerian theory), whereas the 2nd order Eulerian solution does not fare well at all. From this study.
Movie of the reionization of the second electron of helium by quasars, an important phase transition in the history of the Universe. Each panel is 400 comoving megaparsecs across, and would subtend 3.5 degrees on the sky. The left panel is the fraction of helium that is doubly ionized, and the right is the temperature (note that black regions represent < 10^4 K and white represent > 2.5x10^4 K). The movie starts at z=6 and ends at z=3, and it assumes isotropic emission and that the quasars have lifetimes of ~100 million years. See this paper for more details.
Movie of the reionization of hydrogen in a 100x100 comoving megaparsec slice of the Universe (from this paper). These movies were made from snapshots from a simulation in which photons from dwarf galaxies within >10^9 solar mass halos sourced the ionizations. The colored regions in the left panel show ionized hydrogen, with the yellow/green (light/dark blue) regions representing ionized overdense (underdense) regions. The black regions represent neutral hydrogen. The right panel shows the evolution of the 21cm dimensionless power spectrum during this process. Efforts to detect high-redshift 21cm emission will not be able to make images of the signal like seen on the left and instead will attempt to constrain reionization by measuring the shape and evolution of the power spectrum.
Movie of the effect of reionization on the statistics of Lyman-alpha emitting galaxies, from this study. Each panel is 100 comoving Mpc across and 40 comoving Mpc in depth and is calculated from the above reionization simulation. The left panel is the projected ionized fraction, the middle is the spatial distribution of Lyman-alpha emitting galaxies above a Lyman-alpha luminosity threshold and ignoring scattering from neutral gas in the IGM, and the right is the distribution that would actually be observed above this luminosity threshold during reionization. An emitter must be in an ionized region of size >1 proper Mpc for the photons to be not scattered by intergalactic neutral gas. As reionization proceeds in the movie and the ionized regions grow larger, more Lyman-alpha emitters are observed. This modulation can be used to study reionization. For example, the distribution during reionization (right) is more clustered than the intrinsic distribution (center).
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The two movies above are of a 0.3 comoving megaparsec patch of the Universe made with simulations run with the GADGET code. The movies start at z=100 and end at z=15, are linear in time, and show the log of the gas density. In the movie on the left, the gas has not been given a relative velocity with respect to the dark matter, whereas in the movie on the right the gas is moving rightward at a Mach number of 4. (This Mach number stays constant with time at the cosmic mean density owing to how temperature and velocity redshift.) About 5% of the Universe would have had Mach numbers greater than 4. These simulations are the first to include the velocity difference between the baryons and dark matter in a consistent manner. At early times, you see small fluctuations (with an RMS of ~ 10^-3 in the baryons) which grow into order-unity fluctuations by the end of the movies. The shapes of structures are radically changed in the case in which the baryons are moving supersonically, being notably more filamentary (even at z=100).
Movies made from the simulations discussed in arxiv:1204:1344 and arxiv:1204:1345 in collaboration with Ryan O’Leary.
The above movies pan across a very tiny 70 comoving kpc GADGET simulation (the z=20 snapshot) on the left and a 140 comoving kpc Enzo simulation on the right. The gas is moving to the right in both simulations with Mach number 4, and you can see that there are cone-like shock fronts that appear, sourced by the gas moving supersonically past collapsed structures! These cones engulf the volume during the Dark Ages of the Universe. The mass in these cones is pulling on the dark matter, causing the gas and dark matter to come into the same frame via this dynamical friction. In our simulations, a significant fraction of the gas has decelerated into the dark matter frame because of this process by z=20 (including essentially all of the overdense gas).
Movies made from simulations discussed in arxiv:1204:1344 and arxiv:1204:1345 in collaboration with Ryan O’Leary.
Movie shows a montage of the most massive halos in the simulation (10^5- 10^6.5 Msun), in order of decreasing dark matter halo mass. Each panel is a 70 comoving kpc zoom-in slice through one of these halos in the 0.7 comoving Mpc GADGET (top panels) and Enzo (bottom panels) simulations. The center of each panel is at the gas density peak within the halo. The first stars in the Universe are expected to form in >~10^5 Msun halos, and note that the relative velocity of the baryons (moving to the right with the specified Mach number) has a large impact even on the most massive halos that are shown. A mach number of 1.9 is typical, but this Mach number fluctuated spatially on 10-100 comoving Mpc scales with standard deviation of approximately 1 (and a Maxwellian distribution).
The above is similar to the movie on the left, but instead showing temperature and entropy in the Enzo simulation at z=20. The virial shock (and the morphology of the halos) is significantly impacted by the streaming baryons (again flowing to the right). We find that its effect is significant even in cases where the circular velocity of the halo is an order of magnitude larger than the relative velocity of the gas. These halos have circular velocities of 2 to 7 km/s, and the streaming velocity of the baryons is 0.6 km/s.
Okay, this movie is not super serious. It is the byproduct of a long-term project of mine to understand the gravitational relaxation process that leads to cosmological halos. The aim is to understand how this relaxation leads to the “universal” NFW density profile that is ``observed’’ in cosmological simulations.
The movie is of a collapsing cubic perturbation in an Einstein-de Sitter Universe (i.e. Ωm =1) , initialized with full 1st order Lagrangian perturbation theory (and the gravitational field is periodic on the box scale). I find it amazing how this idealized initial configuration goes through complex, but still highly symmetrized, states.