PCS 581 Lecture Notes - Lecture 9: Hot Jupiter, Protogalaxy, Astrobiology
Lecture 9:
Last Class: Quasars
When discovered we didn’t know what they were
Quasars put out lights across the entire spectrum
Every galaxy has super massive blackhole – and when they are active they feed and fire
off jets (when things get stuck in the magnetic field)
Gas fired out and putting out radio
The Black Hole
Are they the brightest thing in the universe?
Brightest things in the universe. Are the Black Holes themselves visible?
The black holes aren’t visible
Irony of quasars – invisible thing in the universe putting out the brightest thing in the
universe
Switching it On
All galaxies have a supermassive hole
oProportional to their bulge’s mass
Why are some active, and some (like ours) dormant?
Depends on their feeding
Every universe have them
Why are some BH is galaxies active and others not – could be due to collisions (make a
ton of gas and flow it down to the black holes) – collision galaxies would result in active
galactic nucleus
Active Galactic Nuclei
Active galactic nuclei are seen in Seyfert galaxies
Cause the enormous jets from radio galaxies
Must be the cause of quasars as well...
Types of AGN
Which are the farthest, on average? Quasars
Which are the most powerful, on average? Quasars
Which have the really huge, impressive jets? Radio Galaxies
Which are mostly regular galaxies aside from a very bright center? Seyfert
find more resources at oneclass.com
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Blazers
The brightest quasars
Pointed right at us
There are other sub groups
Blazars are the brightest quasars because they are pointed directly at us – where the jet
is directly pointed at us
Blazers, Quasars, Radio Galaxies
It greatly depends on our POV
A lot of this depends on the point of views
If seeing edge on you see a lot of things between you and the light so won’t see center
(even if bright) but will see the jets fired – that would be a radio galaxy
If from an angle you will see a bright center: could be Seyfert or Quaser
Viewing will influence what we perceive
Active Galactic Nuclei
Nearby Seyferts and radio galaxies are powered by the same thing as quasars and
blazars
But why are quasars 10x more powerful?
And why are they seen mostly at enormous redshift?
They are all the same thing: feeding black hole
However, Quasars are more powerful (10x more powerful) – because can be seen from
a farther distance
The Protogalactic Cloud
An early gas cloud collapses down
First stars born are enormous, die fast, leave enormous black holes
Black holes merge, gobble up more material
Formation is then guided by the central supermassive black holes
Determines the fate of the
eventual galaxy’s central bulge
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find more resources at oneclass.com
When a galaxy forms, protogalactic clouds – first stars are full of He and they are big and
die quickly so very early on you have blackholes and feeding
As big as they are, they are a very small portion of what there are
The gravity will have stuff falling towards the center and ultimately it and therefore
black hole will fall roughly in the center
If this were to be a spiral – than the black hole with stuff around it would be the bulge
The bulge is roughly the same mass as the BH – reason would be that they were formed
around the same time and later stuff surrounded it and formed the disk
A Tight Relationship
Mass of the central bulge directly related to the mass of the BH
For elliptical it’s the mass of the galaxy
For spiral it’s the bulge
Makes sense that galaxy with the large central bulge would mean it was formed early on
and would have the same mass as the BH
Early Day
Collapse, infalling matter
Merging protogalaxies and black holes
Early supermassive black hole epic meal time
oUniverse was smaller, galaxies closer together
oMergers were much more common
oQuasars were 1000x more common than now
oRare even then, but very noticeable
Collapsing cloud, building black hole
In the early days, you are feeding it with a lot of things when forming the galaxy
They were fed and fed ultimately making them they supermassive black hole
It is when they grow
Universe was denser and galaxies were closer together and mergers were common and
therefore BH common and they were feeding a lot at that time and therefore Quasers –
reason why quasars are very powerful
Collisions resulted in feeding of BH and resulted in more Quasars hence they are very
powerful
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
When discovered we didn"t know what they were. Quasars put out lights across the entire spectrum. Every galaxy has super massive blackhole and when they are active they feed and fire off jets (when things get stuck in the magnetic field) Gas fired out and putting out radio. Irony of quasars invisible thing in the universe putting out the brightest thing in the universe. All galaxies have a supermassive hole: proportional to their bulge"s mass. Why are some bh is galaxies active and others not could be due to collisions (make a ton of gas and flow it down to the black holes) collision galaxies would result in active galactic nucleus. Active galactic nuclei are seen in seyfert galaxies. Must be the cause of quasars as well Blazars are the brightest quasars because they are pointed directly at us where the jet is directly pointed at us. A lot of this depends on the point of views.
