Now, you may remember that there is a
number of scaling relations between
properties of galaxies and their central
massive black holes, whether or not
they're active.
Today, they're mostly inactive.
And these are pretty good correlations.
That, properties of galaxies are measured
of scales of kiloparsecs, or tens
kiloparsecs.
Super black holes are on the scales of
microparsecs, and so it's puzzling.
How can there be such great correlations
over such disparate spacial scales.
So this already suggests there has to be
some connection, interplay between galaxy
formation and evolution and formation and
evolution of the super massive black holes
which occasionally manifest themselves as
active galactic nuclei, more so at high
redshifts then today.
Well, there is an interesting approach to
this.
You can integrate quasra luminosity
function as a function of time now that we
measured it.
And add up all of the quasar like, by like
I mean things like radio all the way
through gamma rays, ever emitted, and then
you can assume that there was certain
efficiency of a creation, you remember is
estimate to be about 10 percent.
So about 10 percent of all the rest mass
that was a created into black holes.
Was turned into the luminosity that we
just added up and the rest is now in form
of the black hole masses.
So that implies that today there is
certain mean density of super massive
black holes, which is of the order of some
hundreds of thousands of solar masses per
cubic megaparsec, and when you compare
that with number densities of galaxies,
essentially it implies that on average
typical galaxy like L star galaxy and a
milky way type galaxy will have about 10
million solar mass black hole in it, and
milky way has three or four million solar
mass black hole.
Andromeda has some of the bigger one and
so on.
So, just from adding up the quasar light
we can say something about volume density
or abundance of black holes today.
And indeed we find out from the
correlation between masses of black holes
and their host galaxies' luminosities, or
stellar masses, but approximately 0.1
percent of the host galaxy is mass, or
other, or the old stellar component of the
host galaxy mass is turning to the black
hole.
And that turns out to match exactly within
the arrow bars.
The argument from adding up the quasar
light.
So this is good.
This is completely indepenedent argument
and we reach the same conclusion.
So it's indicative that we actually got
the story right.
So super massive black holes are
ubiquitous.
They occured in essentially all massive
galaxies.
Not so much in dwarfs.
And they're just normal phase of galaxy
evolution.
Now remember, the way to fuel active
nuclei is the same way as to how to
trigger bursts of star formation and that
is through dissipative merging.
Gas loses energy very effectively, sinks
to the middle where it can trigger star
formation or it can fuel super massive
black hole.
So this physical process can account for
simultaneous growth of both galaxies with
their stellar components, as well as their
super massive black holes.
And indeed we can model the process now in
computers and hydro simulations.
This is a montage of phases of merger of 2
spiral galaxies each of which has a black
hole and, and so on.
And.
The same process of hierarchical
disability emerging then creates both
continues distribution of both galaxies
and super-massive black holes.
So that alone can drive some of the
observed correlations, but there is
another component to this and this is so
called AGN Feedback, not only is the input
important but also the output.
Active nuclei can easily ionize
intersteller medium of their host
galaxies.
Now that can actually stop star formation.
So energy input by active nuclei can
regulate star formation in their hosts and
if there's a lot of it, it you can cut it
off.
Also, there is a mechanical luminosity, as
you recall.
All these relativisitc electrons streaming
out through jets and so on and that
mechanical luminosity can match
electromagnetic luminosity.
So over typical lifetime integrated
episodes of.
Active nucleus activity it may release of
the order of 10 to the 60th ergs in
luminosity or mechanical energy.
Recall also that the binding energy of an
averge galaxy is more of the order of 10
to th 59 ergs.
So even if small percentage of the energy
generated by active nucleus is coupled
somehow to the material in the galaxy
itself, it can make profound effect on
galaxy structure and growth.
And we now think that this is what's
happening, so it's this feedback mechanism
that sharpens up the correlations that are
observed.
These are snapshots from a simulation but
trying to reproduce growth of a really
massive black hole that ignites as quasar
at around redshift of 6 or a little
higher.
And it is possible to pile up enough
material quickly enough through
dissipative merging to actually generate
these objects at the time scales that
correspond to when we observe them.
They are rare.
These are like the most massive objects in
universe at the time but they can exist.
And so what's emerging today is a picture
of quazar galaxy or super massive black
hole galaxy co-evolution and co-formation.
They're both assembled in a similar
fashion through hierarchical growth,
quasars can exert feedback onto their host
galaxies.
The two processes are tightly coupled, so
these extreme objects or events are really
part and parcel of the overall evolution
of galaxies.
And the next time, we will talk about the
origins of those first super massive black
holes.