Future Evolution of the Intergalactic Medium in a Universe
Dominated by a Cosmological Constant

Kentaro Nagamine & Abraham Loeb
Harvard-Smithsonian Center for Astrophysics

2004, New Astronomy, 9, 573

[ paper with high-resolution figures: gzipped postscript (683KB)   PDF(554KB) ]


[See also a companion paper on the Future evolution of nearby large-scale structures in a universe dominated by a cosmological constant]

We simulate the evolution of the intergalactic medium (IGM) in a universe dominated by a cosmological constant. We find that within a few Hubble times from the present epoch, the baryons will have two primary phases: one phase composed of low-density, low-temperature, diffuse, ionized gas which cools exponentially with cosmic time due to adiabatic expansion, and a second phase of high-density, high-temperature gas in virialized dark matter halos which cools much more slowly by atomic processes. The mass fraction of gas in halos converges to ~ 40% at late times, about twice its calculated value at the present epoch. We find that in a few Hubble times, the large scale filaments in the present-day IGM will rarefy and fade away into the low-temperature IGM, and only islands of virialized gas will maintain their physical structure. We do not find evidence for fragmentation of the diffuse IGM at later times. More than 99% of the gas mass will maintain a steady ionization fraction above 80% within a few Hubble times. The diffuse IGM will get extremely cold and dilute but remain highly ionized, as its recombination time will dramatically exceed the age of the universe.
slice gas temperature gas mass dark matter

The above movies show the evolution of projected distribution of mass-weighted gas temperature, gas mass, and dark matter mass in a comoving 50x50x10 Mpc/h slice. The above is the same slice as the one shown in the paper.
  The clock shows from left to right, the snapshot number, scale-factor, redshift, and the cosmic time in units of the current Hubble time tH=14 Gyr (for h=0.7). The reionization takes place at z=6 in this simulation. As we showed in Nagamine & Loeb (2003, New Astronomy, 8, 439), the dark matter mass distribution hardly evolves after t/tH=3.0. You'll see that the temperature quickly decreases after t/tH=3.0 due to the exponential expansion of the universe.
   The clock and the pictures may not synchronize well depending on your download speed. The movies tend to get behind of the clock by 1-2 frames if your download speed is slow. The temperature movie goes all green suddenly at z=6, so you'll know when you're out of sync. I've disabled the looping of the movie to avoid accumulating the sync. If you're out of sync, wait for the first movie to finish, and click `Reload' or `Refresh' to see it from the beginning again. (But I've found that they sometimes don't behave as I wanted to. For example, the Netscape on my Mac laptop doesn't bother to reload the movies when I click `Reload'. The results are perhaps browser dependent, and IE seems to work well.)

Want to see more? Here are other slices.
Slice 0    Slice 1    Slice 3    Slice 4

Romanian translation courtesy of EWS Translate