Lecture 3 Notes: Magnitude Systems
Before we can discuss galaxies quantitatively, we must rst introduce some new terms. The specic
~
intensity I() is a measure of energy ux incident on a unit surface area per unit solid angle and
2
frequency (erg/s/cm /st
Lecture 1 Notes: Intro to Course
1.1
Dynamics of scattering
A natural way to begin is to ask the seemingly naive question what is a galaxy? The
straightforward answer is that a galaxy is a system of stars and gas, like the Milky Way (the
word galaxy comes
Lecture 8 Notes: Box Orbitals
For orbits in a non-axisymmetric potential, no component of the angular momentum is
conserved. There are nonetheless two distinct families of orbits that contribute to the shape of
the galaxy. The families are generated by st
Lecture 4 Notes: Gravitational Theory
The central result of Newtons gravitational theory is the inverse square law two
point masses m1 and m2 separated by r = x1 x2:
Gm1m2
for the force between
(1.32)
F(r) =
r2 r.
Since the inverse square law can be added
Lecture 6 Notes: Inverse Radius
Our method for building galaxy models (often called Schwarzschilds method, after Martin Schwarzschild, son of the general relativist Karl)
requires that we construct an orbit library in which we store the footprints or prob
Lecture 5 Notes: Long Axes
Recall that the first step in constructing a galaxy is to pick a gravitational potential. Since dieren- tiation is generally much more
manageable than integration, it should be no surprise that we rely on Poissons Equation to ge
Lecture 10 Notes: Jeans Equation
Jeans equation applied; Jeans theorem
1.11
Many if not most galaxies appear to exhibit cylindrical symmetry. Following the outline given above for obtaining Jeans equations in
spherical coordinates, one can obtain the cycl
Lecture 9 Notes: Simplifying Assumptions
We start by writing down the collisionless Boltzmann equation (1.119) in spherical coordinates (r, , ):
f
f
t + r
r
+
f
f
f
+
f
+ vrvr
+ v
v
f
+ v
v
= 0,
(1.136)
where the time derivatives of the coordinates may
Lecture 2 Notes: Gravitational Potential
As we saw above, gravitational scattering plays a very small role in the dynamics of stellar
orbits within galaxies or globular clusters. We return to our original question, what is a galaxy?
In light of the previo
Lecture 7 Notes: Vector Equations
We have seen above that empirically, most galaxies are not spherically symmetric, but rather have flattened disks or ellipsoidal shapes.
For many of these more general potentials, azimuthal symmetry and also up-down symme