Video Gallery

Video Gallery: Galactic Mergers

Select videos by clicking on the numbers below. Mouse over the running videos for brief descriptions. [More information/credits.]

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More Information/Credits

Here's a bit more information on the simulations in the slide show.

Slide 02. Perspective author Joel Primack, along with Patrik Jonsson (now at the Harvard-Smithsonian Center for Astrophysics) and Greg Novak (now at the Department of Astrophysical Sciences, Princeton University), developed this movie showing a simulation of a pair of merging spiral galaxies as they would appear through a telescope -- including the effects of gas cooling and heating, star formation, supernova feedback, and absorption of light by interstellar dust. The movie runs through three billion years of simulated galactic history in around a minute and 20 seconds; regions containing young stars are bright blue, while dust absorption causes some areas to appear darker and reddened. The movie was recognized as a semifinalist in the 2008 Science/NSF Science and Engineering Visualization Challenge. [More information on YouTube site.]

  • Credit: Patrik Jonsson, Greg Novak, Joel Primack, University of California, Santa Cruz

Slide 03. Frank Summers of the Space Telescope Science Institute used simulation data from Chris Mihos (Case Western Reserve University) and Lars Hernquist (Harvard University) to create a movie showing a full collision sequence. At various stages during the simulation, the movie stops, and the image from the simulation is compared with an actual observation of a galaxy collision at a specific stage, captured by the Hubble Space Telescope -- thereby rooting the simulation in actual observational data. [More information at HubbleSite.]

  • Credits: NASA, ESA, and F. Summers (STScI)
  • Simulation data: Chris Mihos (Case Western Reserve University) and Lars Hernquist (Harvard University)

Slide 04. Tiziana Di Matteo, Volker Springel, and Lars Hernquist created this computer animation showing the evolution of a galaxy collision simulation; in contrast to the previous two simulations, this one includes the effect of supermassive black holes hosted at the center of the two galaxies. The simulation, which shows only the gas distribution of the two galaxies, covers a period of 2 billion years; brightness represents gas density while the colour hue indicates gas temperature. [More on T. Di Matteo's Web page.]

  • Credits: Tiziana Di Matteo, Volker Springel, Lars Hernquist. Posted with permission of T. Di Matteo.
  • Related paper: T. Di Matteo, V. Springel, L. Hernquist, Energy Input from Quasars Regulates the Growth and Activity of Black Holes and Their Host Galaxies, Nature 433, 604 (2005).

Slide 05. Video from Philip Hopkins, now with the U.C. Berkeley Astronomy Department, and Volker Springel, University of Heidelberg, shows a simulation of the merger of two Milky Way-like disk galaxies, with a 2:1 mass ratio; the properties of the galaxies include stellar and gas disks, central spheroidal bulges, and black holes, within a dark matter halo. This video shows stars rather than gases; the color shows the mean stellar age -- from 10 million years (blue) to ~1 billion years (red) -- while brightness shows the projected stellar surface density, scaled logarithmically. [More information on P. Hopkins Web page.]

  • Credits: Philip F. Hopkins, Miller Fellow, Department of Astronomy, U.C. Berkeley; Volker Springel, Professor in Theoretical Astrophysics, University of Heidelberg/Heidelberg Institute for Theoretical Studies, Germany. Posted with permission of P. Hopkins.

Slide 06. Thomas J. Cox, of the Carnegie Institution, simulated the interaction and merger of two Milky Way-type galaxies over a 3 billion year period, with the simuation showing stars rather than gases. Tidal forces create long tails as the galaxies pass close to one another; such interactions are considered to be significant drivers of galaxy evolution, and likely trigger bursts of star formation, excite accreting black holes, and change galaxy shapes from spiral to spheroidal. In this simulation, the movie is "stopped" at 2.33 billion years into the simulation, where it closely matches an actual image of the first-observed binary quasar -- a pair of accreting black holes discovered by the Sloan Digital Sky Survey.

  • Credit: T. J. Cox, Carnegie Institution. Posted with permission of T. J. Cox.
  • Related paper:P. J. Green et al., SDSS J1254+0846: A Binary Quasar Caught in the Act of Merging, Astrophysical J. 710, 1578 (2010).