The next level of sophistication is
introducing barriers, gas and dissipative
processes that must effect it. Including
things like star formation and energy
input by star's formation of. Black holes,
there activity is active galactic nuclei.
There feed back through energy input in
the surrounding gas, and so on. These are
far more demanding technically, and it's
only in recent years that we had
simulations good enough to really compare
to observations. The key problem is the
nomical range. A lot of dissipative stuff
happens on very small scales. Scales of
stars or interstellar separations. Which
are of the orders of parsecs, and yet we
want to look at regions of the universe
that are megaparsecs or even gigaparsecs
in size. So it's simply hard enough to
achieve sufficient numerical resolution,
that will cover both Scales, and truth be
told, sometimes we don't really understand
how some important processes work. We have
pretty good idea how stars form, but not
in a really excellent detail we would
like. So next movie, we'll take a look at
a formation of cluster of galaxies using
full hydro code, again by the Max Planck
Group, and showing how different physical
properties change in time. Now, here we
start at the redshift of 20, when just see
the 1st large scale structure formed The
different panels show different
components, the density of the dark
matter, the density of baryonsal gas, the
temperature, shock waves and predictions
for senia zubovich effect. Note how
similar yet in detail different structures
are as you look at different physical
properties of these. Cause their proper
only forms at the redshifts of a few. Now
you begin to recognize that this could be,
in fact, a cluster. But if you had eyes
that could see both dark matter and hot
gas, this is the comparison of things you
would see. Now, look at behavioral gas. It
is heated by the shocks of the falling
pieces as they collide kenetic energy is
transferred into radiation which heats the
gases up, this is why clusters are filled
w ith extra gas Introducing dissipation,
opens much richer physics. It can see
many, more phenomena than you could
possibly see, with just the old dark
matter simulation that only had gravity.
Here we're going to zoom in on different
physical properties in, In order first
zooming on one and then the other. Note in
detail how different structures are, and
especially the richness of structures that
show up in the extra gas. Specialists say
big pieces fall in and they heat the gas
creating shock waves and like cometary
trails. Here it's the same sequence but
zooming in on a different portion. So you
can see spherical uniform homogeneous
model does not really seem to respond well
to reality. Our spherical top half model
was a useful toy model to understand the
basic physics or the collapse of density
flucuations. But the reality is much more
complicated. And this is why we need to
use numerical simulations to actually
figure out what's going on. , Again, these
simulations produce a wealth of
information that can be mind in detail.
These are just some snapshots from
cosmological simulation again, from Max
Planck Group. You can see that there's
familiar structure of cosmic filliments
and so on, and voids. But now, There is
much more at play here with gas reacting
to the feedback from stars, collisions and
so on. It is this kind of simulation that
actually is getting us really closer to
understanding the formation of Earth
galaxies. Let's go back to the old problem
of colliding spiral galaxies. How embody
simulation really started. Now we can
collide galaxies that have multiple
components. Dark matter, gas, stars, or
even black holes, and what they're seeing
in simulations like these, dark matter
behaves pretty much in the way we've seen
before, but the gas dissipates energy and
That makes it collide and collaspe much
deeper much faster, because gas can
disapate energy it goes deep in potential
oil. It becomes denser and can cause a
burst of star formation or feed super
massive black whole if one ex ists causing
activity of quazar nature. Some of us end
with a movie of colliding spiral galaxies
that include dark matters, stars, gas. In
each of the two galaxies has a big black
hole in the middle, which then gets fed by
the gas and simulation and feeds back
energy, radiation and kinetic energy input
into the gas itself. Let's take a look.
There are two identical models for our
galaxies, and as they collide, first you
see the usual tidal distortions. Things
will look very symmetric, because the two
galaxies were intentionally made to be
identical at start. This provides an, a
useful check on consistency, because you
expect to see things be exactly symmetric,
until things get more complicated, with
input of energy from distributive
processes later. Right now.
This is just the first passage there is
already some feedback of gas being heated
by the collision and now the black holes
ignite, both galaxies now have active
nuclei that causes shock waves and
expansion of gas away from the system.
Some of the gas keeps collapsing. It feeds
more of the black hole activity in the
middle. Which can reignite again, and this
is how octave galactic nuclear is supposed
to work. In the end, you can see a very
dense distal gas. You don't see the black
holes, of course. And this Is getting very
close to our understanding of the origins
of the nuclear activity of galaxies in the
universe. So this is our theoretical
understanding of the formation of large
scale structure in this evolution in the
universe. Next, we will start talking
about actual observations of the large
scale structure.