ASTR 1200 Announcements

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ASTR 1200Announcements
Exam 3 Returned Today Two more lectures in
B180 after this. Final Exam Wednesday Dec 17
130-400 In Benson 180
Website http//casa.colorado.edu/wcash/APS1200/AP
S1200.html
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The Distance Scale
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Redshift of Galaxies
Hubble found that galaxies are redshifted. The
absorption lines are those of the stars that make
up the galaxy.
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The Redshift
z 0 implies local z of 1 or more implies near
far edge of universe
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Hubbles Law
The more distant the galaxy, the greater the
redshift. The more distant is the galaxy, the
faster it is flying away from us.
H070 km/s/Mps
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Example
Galaxy in Virgo Cluster is at 15Mpc
will recede at v 70 km/s/Mpc x 15Mpc 1050km/s
dl l x v/c 4000Å x 1050/300,000 14Å
a 4000Å line will appear at 4014Å
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Example 2
l0 1216Å but is observed at l 1228Å
dl 12
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A Modern Hubble Diagram
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Galaxies are Flying Apart
Galaxies remain same size. They just get farther
apart.
Effect is the same no matter which position you
occupy
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Expanding Universe
Current Universe
The volume of the universe is increasing.
Early Universe
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The Age of the Universe
Notice At time zero, d 0 All galaxies are at
zero distance! The universe has zero
volume! when t1/H
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The Beginning
Before 13 billion years ago, there was no
before. Time and space started with the Big
Bang We will return to this in a few more
lectures
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Galaxies are Moving
Gravity attracts them to mass centers.
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Redshift Survey
The Great Wall
Galaxies across the sky. Distance from redshift.
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More Galaxies
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The Texture of the Universe
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Theory of Structure
Structure grew out of minor fluctuations. Gravity
causes density regions to enhance. The very
origin of structure.
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The Cosmic Web
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Active Galactic Nuclei

• Seyfert Galaxies 1948
• Radio Galaxies 1954
• Quasars 1962
• BL Lacs 1968
• Blazars 1980
• Theyre all manifestations of the same thing.

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Seyfert Galaxies
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Quasar
QUAsi Stellar Radio source ? Quasar (Sometimes
QSO) Completely enigmatic 1960-1980
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Huge Redshifts
The Brightest Objects in the Universe
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Quasar Spectrum
Originally found from radio But not all have
radio. Broad spectral output from radio to
gamma-ray
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In a GalaxyFar, Far AwayLong, Long Ago
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The Most Distant Quasarz5
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Host Galaxies
Quasars are in host galaxies Mostly just outshine
the entire galaxy
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The AGN Model
The Nucleus of the Galaxy is the Clot of
Stars around the giant black hole thats fallen
to the bottom of the galaxy gravitational well.
As more material falls in, the black hole grows
and the nucleus can get very bright.
I think all major galaxies have a BBH (big black
hole) in the center. This is yet to be proven.
Certainly a substantial fraction do.
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Feeding a Quasar
Accretion disk is formed of stars and clouds that
wander too near the big black hole. Tidal forces
rip them apart. They settle into an accretion
disk. When theres no material falling in, the
quasar goes quiet.
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Spectrum
Width of line implies velocities of 30,000km/s
! High Orbital Speed implies deep gravitational
well.
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AGN Accretion DiskSimulations _at_ 0.1?as
Courtesy of Phil Armitage, U. Colorado and C.
Reynolds, U. Maryland
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Jets
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Jets
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Fields Twist to Make Narrow Jet
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Radio Galaxies
Very Large Array
Very Large Baseline Array
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Cygnus A
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Radio Lobes
Lobes contain 1053 Joules of energy in
relativistic electrons. Mass energy
equivalent of a million stars!
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Wind Blows Jets
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Full Model
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Superluminal Expansion
Radio interferometers see blobs emitted by AGNs
from base of jet.
Watch them expand. Know distance, so can measure
speed. v 900,000km/s v 3c Superluminal !
? Is Einsteins ghost worried?
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Phase Velocity
Point of impact can move v gt c Nothing traveling
that fast.
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Better Explanation
Blob moves close to speed of light toward us. Its
closer later. Makes sideways motion appear
speeded up.
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Quasar Absorption Lines
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The Intergalactic Medium
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Intergalactic Medium
70 of the regular matter in the universe is
between the galaxies Was probably neutral, then
re-ionized Somehow got oxygen and other heavy
elements. We didnt know it was there 20 years
ago. Still dont have any clue how it
works. Cutting edge of research.
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The Cosmic Web